Based on experience!
There are lots of things you can do in brewing, but what people forget is that there is always a consequence.
Whether it is enough to affect what you think of your beer is perhaps a different question, but someone (say a beer judge) tastes your beer and goes "a bit hazy -one" "not really clean finishing -another point or two" "Touch of DMS, not to style -another one"... Pretty soon a good solid beer is out of the running.
If you have ever read the response to comps, you will see lots of whinging about how poorly peoples beer has done compared to what they expected, how it went in a local comp, the state comp.
Seriously people forget the law of unintended consequences - everything you do ends up in the glass, choose the cheapest malt V the best malt for a job (i.e. Belgian Pilsner when making a Belgian Triple) it wont taste the same, not saying it will taste bad, just less like the beer you are modeling.
Badly adjusted mills give you lower yields. You have to buy more malt to reach the same OG, lautering will be slower (or too fast), you may well get more tannins as the husks are shredded more...
Shorten the mash time, you will have a higher proportion of unfermentable dextrins, (can be measured)
Shorten the boil, you wont (can't) get the SSM>DMS>Removal that you get at a longer boil, you will get more DMS. Whether or not that matters to you is again a different question, but you will have more DMS.
You wont get the optimum removal of high molecular weight protein, which will affect clarity, mouthfeel and stability (not might will - in measurable ways)
Pitch less yeast - well we could go on but why.
If you think shortening your mash and boil wont have an effect on your beer you are wrong, it will. The only question is whether or not its going to affect your drinking pleasure (which becomes a question about your palate).
If the only beer you want to make is IAPA where you cant taste anything other than hops, well you will probably get away with it.
Locally I have about half a dozen commercial breweries that I'm familiar enough with to say with confidence that they all mash and boil for 60+ minutes and mostly boil for 75-90 minutes.
Is it reasonable to think that professional brewers at least double the mash/boil time because they are all stupid/ignorant, or that they know the benefits and are prepared to invest the time and money to make better beer?
Worth noting that wort boiling is the biggest energy consumer in brewing, if it was possible to make good beer with half the energy cost - do you really think no one in the industry would have noticed.