Jason Liang
why is it so hard to play defensively in sf5?
honest answer is: capcom wanted to make the game faster, flashier and 'punchier' than sf4 so that it would look more appealing when viewed by non-fighting game aficionados during eSport events.
there are a ton of technical reasons why, and i outlined a few in previous posts breaking down sf5's style of play, and the video of the priority system posted above further showcases the design philsophy by the design team to have (in theory) matches become much less about 'set play' and 'knockdown vortex' (i.e. SF4 meta-game) and more about what is simplified as "rushdown" play.
the fact that it has a huge buffered input delay, as i mentined in a previous post when we were talking about how sf5 is so 'slow', also makes it much, much harder to play Defensively specifically because it is much harder to play in a "Reactionary Style", i.e. literally harder to react in time to your opponent's bullshit be it a jump-in from them or be it them spamming one f their heavy pokes.
I assume you've also noticed SF5, in general, everything does a lot more damage-per-hit, right? that also has to do with it.
it is simply a better risk/reward ratio to attempt to jump at you 5 times in a row, because if even if you anti-air me 4 of thse 5 times then the 1 time i manage to land a jump-in combo on you will allow me to inflict 45-55% damage, sometimes more.
simply put: thoughtless offense nets a bigger reward than inscrutable defense in sf5.