It's not necessarily about counterability, either – it's about keeping the metagame balanced and teambuilding variable. For an example, look at Gen IV prior to Garchomp getting banned. Garchomp was so strong and so prevalent that any team that didn't carry a dedicated counter got crushed. Teams that carried Garchomp (that being the majority) started carrying counters to their opponent's Garchomp and adding counters to the opponent's possible Garchomp counters, and so on and so forth. In the end, what you got were a huge number of teams that consisted only of Garchomp, 1-2 Garchomp counters, 2-3 counters to their Garchomp counters, and maybe a single wildcard Pokemon.

See how stale and boring that would get, fighting almost the same teams every time you booted up ShoddyBattle? And bear in mind, that's with something that had counters! Banning Garchomp allowed far more varied teambuilding, because you were allowed to use a wide variety of Pokemon and still be successful, instead of being limited by one super-powerful, ever-present Pokemon.

MegaBlaziken and most of the other quickbanned Pokemon of this generation are the same way. Sure, I can understand in the short run why it might suck, but (at least I think) maintaining the metagame in such a state that diversity in teambuilding is maximized makes for more entertaining battles.

As Mikedroid said, there's a different between a check and a counter.
A check is something that is capable, given a free switch-in (such as after you've lost something or used a slower VoltTurn move), of forcing out or KOing a given Pokemon in even the worst-case scenario, not factoring in bad luck (i.e. the move missing or the opponent getting a critical hit).
A counter is something that can manually switch in and force out or KO the opponent even in a worst-case scenario – again, not factoring in bad luck.

Crawdaunt is not a counter to MegaBlaziken, as it can't be manually switched in safely. It is, at best, a check – and it fails even at that if any form of entry hazard is up, which it almost always will be.

More to the point, though, calling the guys at Smogon responsible for tiering "lazy" for banning stuff is a little ignorant. I mean Christ, look at the kind of time and effort they put into the whole thing. You can call people with that kind of dedication a lot of things, not all of them good, but "lazy" isn't one of them.
(moar next post)