In order to understand the Parry's effect on close quarters combat, you have to understand the theory behind Street Fighter's footsies (in non 3s games that is.)
In SF, the counter to a blocking opponent is to walk up and throw them. The counter to that is pressing an attack button to prevent the throw from occurring. Here then is where footsies begin. In close range, the tension arises from two players trying to figure out when the other person is going to press a button. The player pressing action has two options, either to walk forward in range and press a button right before the other player does and thus hitting them, or walking in then back outside the other players max distance right after they whiff an attack and punishing accordingly, AKA whiff punishing. The counter to whiff punishing then, is walking forward.
Ok now HERE is where parries come into play. Walking forward presents a risk in both options. To the offensive player, you face the risk of getting hit by a poke, to the player countering the whiff punisher, you risk getting hit by him as well. Either way, walking forward in footsies range presents a risk/reward of gaining ground or getting hit. Parries take all that risk and metagame out. The player walking forward with parries has the ability to simply walk forward and mash down without worrying when exactly the other person is going to press a poke attack. The forward walk is protected by parry system since the player can intermittently press down while walking. On the converse, they can stay right outside of footsies range and simply pressing down and walking back/forward. Capcom's intent for their system changed then from a player predicting exactly what the other person is going to do and parrying it, instead to figuring out whether or not the other player is TRYING to parry, because if they want to, then they will.
Now don't get me wrong, I'm not saying one is wrong or the other is right, but 3s doesn't have the footsies game that any of the other SF's had, it's just different. That's also a big reason why a lot of 3s players are 3s players only, and players that played other SF's and preferred them tend to stay away from 3s(ex choi).
