it is an option. usually not the cheapest one, but in quite a few cases makes more sense/convenience compared to flying - ie if you have less than 5-6 hour distance to cover it's faster, plus the hassle of airports, security, baggage limits, ending in the middle of nowhere compared to city centre etc are not that great.
another good thing is, you can buy in most cases tickets just days ahead, most trains have constant prices so your price isn't within 50-1000 eur boundary for same flight, same seat, depending on timing.
I don't really disagree with that. Especially if you're travelling between downtown locations that aren't too far apart on main railroad lines, e.g. York to London or London to Brussels, the train makes a lot of sense. (As indeed is the case in the Northeast US.)
It just isn't the panacea that it often seems to be painted as.
another good thing is, you can buy in most cases tickets just days ahead, most trains have constant prices so your price isn't within 50-1000 eur boundary for same flight, same seat, depending on timing.