[gcl2]

I don't know whether this person is trolling or not but if he's not, I doubt he's going to be good at running a business (might be great at running an app/product though).

While all the stated reasons are correct and beneficial, they are only to one party - the developers themselves. And unless all your money is coming from the developer (which by definition is not), you probably want to care more about what your users need and want rather than tell them what you can and will not support.

Running a business (a profitable one) is all about meeting customers' needs, expectations and wants. No matter how ridiculous they are. No matter if they are wrong and you are right. No matter if they are running your app on a machine from the 90's while you only support the latest and greatest HTML5/Canvas/Node.js/blah blah.

One customer that you don't support is not just one customer that you've lost. It's one customer that you've turned away from your product AND incentivized to spread the bad karma to everyone they talk to about your product. The next time they hear someone discussing your product, they're going to chime in "Yeah, I loved using them until they turned me away by not supporting <whatever version they had>. They don't care about me at all." While this statement is false or at least untrue (I'm sure you care about all your customers right?), the reality is that it doesn't matter. They are spreading a negative review and it's only going to fester and grow from that point on.

So whenever you're ready to build a business out of your successful website/app/whatever, remember that you need to support whoever is ready to pay you. That's all that matters.