I'll add a reason why AG is harder to get into (also makes it easier in a way).
Pros of tins: no further equip req beyond K+K once you have a big pot. Loose ingredients can be purchased in any size (25g - 50g - 100g) packs and simply put in ziplocks and reused later. Doesn't jack the price up much. Spec grains can be steeped easy peasy and purchased in bulk, uncrushed and used as per need.
Cons of tins: Difficult to do small batches unless you have good sanitary ways of storing the tins, or use DME.
Con of doing small scale AG:
1. Just as time consuming as larger batches, so to do a small volume you end up asking if it was all worth it! (With extract its pretty linear, and you skip the mashing or can do it alongside the boil even).
2. Cost of ingredients and/or equipment. Yes, I've heard that you don't need to buy a mill, but how else do you get a good crush?! even with NickJD's method, min need coffee grinder. Else, get HBS to crush grain, that means you can't bulk buy or buy 25 kilo sacks, which actually ends up making AG expensive (buying crushed bagged recipes). I know I paid 18.50 for what was supposed to be 2.7 kilos but actually was 2.9+ kilos of grain this month. Even at 3 kilos, its more than 6 dollars a kilo and in ideal scenarios it should've netted me 14.5 litres of pitchable wort. That could be scaled to say 25 dollars (29.34, but lets say it gets cheaper due to bigger grain bill). at 25 dollars to the grain bill for a 23 litre batch + hops + whirlfloc/irish moss + gas used/electricity it is actually getting uneconomical. Especially beacause of the 25 dollars of grain. The alternative to get the same type of grain crush would be to buy a grain mill and thats $$$ - So, COST IS A REAL ISSUE WITH AG, one way or the other, it costs more. For people brewing 30-80 litre batches, its easy, the equipment quickly pays for itself in malt cost savings.
3. The kitchen mess you make doing stovetop mashes is always a reminder - TAKE IT OUTSIDE. That means more expensive gas + burner outlay. Possible workaround is using the barbecue... hmnn...
Pros of AG for small batches:
1. Can DO small batches (ignoring cost) without having to worry about sanitary storage of goop and LME etc.... quite a lot of freedom in this.
Thing is, a brewer just starting out AG would want to start off small with pilot batches, hopefully and learn the nuances before plunging into big ones (ppl are different, I know, well, this is me)
Also, some would like to keep it small scale anyway, not being a big beer guzzler means I also need to brew a lot less and its beer, not wine, it can only stay fresh for so long! + how much of the same can I drink, need variety. So, milling my own grain would get me over the line nicely, albeit the mill is going to push me down the 'slippery slope' a lot more than 20 dollars, even a coffee grinder costs, a lot less but does cost. Even then, if I buy 2 sacks of malt at bulk buys or even sack price to make my favourite beers and continue to buy spec malts fresh from HBS, at 3 kilos to get 15 litres of beer, that is about 17 brews, that malt will go really stale! Add to all this the hassle of blocking the kitchen up for a good 3-4 hours minimum for a measly 15 litres of wort not to mention the time :S Extracts can be boiled and hopped in 90 minutes, there is no sparge or mash involved and if there is, it can be done alongside, hops can be boiled with the extract. Much shorter process.
I'm not saying all those problems don't have solutions, not that I've found them all yet, but they are reasons why jumping to grain mashing can be quite expensive in overall terms, either with equipment or ingredients.
IN A NUTSHELL: AG is costlier unless you brew bigger batches, and the bigger the batches, the more time you spend brewing and drinking and a lot less doing other things. Not everybody's cup of tea. If equipment like the Braumeister were made more affordably, I can see more people doing it, at least, try on inexpensive equipment to get some confidence and then buy a brewing unit to do it indoors on a small scale, as it exists they are expensive and putting together a rig gets expensive really quickly. A ball valve + fittings costs you a fair bob more than $20 to get a connection between pot and fermenter happening, and you need that to make it less messy/avoid siphoning wort, just an example how the price of small things makes it a lot more expensive. No chilling sounds great in theory but how is a noob supposed to work out the differences to bittering it makes! I'm just trying to make to recipe to get something resembling good beer made! Now you will point me to a brewing software and that again costs $$.
Point is, its going to cost you, a few different ways to tackle it but it still costs you a fait bit of $$, time and effort = Determination, which, well, how many noobs would raise their hands and say they would persist with making it happen! No wonder ppl say *** it and stick to cans = ease + cheap overall.
