Except that you get slow connection speeds pretty much everywhere as soon as you move outside your house. Subways, commutes, etc. For crying out loud, you even go to EDGE on AT&T when commuting in Sillicon Valley on CalTrain!

Probably because you don't know where your app will blow up. Unless the app is geographically restricted, there's no real telling where the spark will happen. Maybe it unintentionally solves a massive problem that is happening right now in India, and you suddenly have a massive influx of 2G users. If you hadn't even considered the experience for them, it won't matter how quickly it blows up; it'll fizzle immediately when you have a shitty experience.

For example, on my trip a few weeks ago, I used T-Mobile's free 2G roaming to get around. Searching for something on Google was pretty quick, and loading a Wikipedia page also was relatively fast. But the second I moved away from them and onto real sites that didn't try to optimize for lower speeds, I was pulling my hair out at how much data was trying to get sucked down on such a slow connection. It took minutes to load some websites.

Happy visitors to your page/app/whatever?

Return visitors to your page/app/whatever?

Just because one is connected using Verizon, doesn't mean the connection speeds at any given time are all that great.

The question is, how do you know how much is to be gained, unless you try? Just because you see most customers being on high speed connections most of the time doesn't mean much: for one, it could be because otherwise it's so bad no one does it; plus, a better experience for slow connections/older devices is quite likely to translate to better experience for everyone.

Otherwise, you might figure it out when you suddenly lose most of your users to a competitor who offers a snappier experience.