2 hours each way is indeed not a very sustainable commute. I had a 90 minute one about every other day for a bit over a year and I wouldn't have wanted to do that long-term.
However, 30 miles is significantly under the average US commuting distance. And, unless you live and work near an urban downtown, 30 miles probably doesn't get you to a lot of appropriate professional jobs. I live in an exurb outside a major metro and my (nominal) office is the nearest tech job I could physically commute to and it barely squeezes in under 30 miles.
Should clarify that I say two hours per day above. I don't think I'd spend two hours going thirty miles, or even necessarily choose a job that involved driving thirty miles every day.
But thirty miles in an hour on urban/suburban rail isn't particularly unusual. And this time is time you can use, if you have even a little bit of method about it. I know people who have done all the reading for entire higher education degrees in that period of time.
At any rate, the notion to which you're responding regarding the area of possible commute being 2800 square miles is foolish. You have to go to where the jobs gather, and there are all sorts of complex reasons why they don't distribute evenly across that area that a rational person should not spend time weighing up when they consider whether an iPad might be a useful thing for the train.
In my case, if I made the commute into London on a daily basis, knocking down the distance to this hypothetical US average of 16 miles might save, I think, about a third of the journey time in practice. It would knock off half of the price of a season ticket, which might be useful. But it would add easily 40% to the cost of a house, which is the overriding concern. And even then I'd still buy the iPad for that journey.
But, yes, other numbers seem to be lower (and are generally more likely to quote commute time rather than distance which is probably more relevant for most people).
However, 30 miles is significantly under the average US commuting distance. And, unless you live and work near an urban downtown, 30 miles probably doesn't get you to a lot of appropriate professional jobs. I live in an exurb outside a major metro and my (nominal) office is the nearest tech job I could physically commute to and it barely squeezes in under 30 miles.