They're following the League of Legends example.
The unlocking of classes is essentially a way to ease players into the fairly complex system that exists once everything is available. Right now, it's not readily seen since Ranked servers aren't in, which adds that second element of placing you with players based on a modified ELO with time played as a major factor.
The switch to items/perks/weapons is a good way to do it without making players feel limited. Too be honest, in pubs, the 'upgrades' don't really make a significant difference at all. The complex loadouts only really matter in comp situations where there are organized strats. For example, the Tech thumper is taken in situations where you are going to be faced with Flag Standoffs (that is, both teams have each other's flag) and you need to be able to bounce it to prevent the enemy from grabbing it once your carrier is killed. I've never seen an organized standoff happen in a pub.
Goal #1 is to get lots of players. In today's competitive environment, you can't do that by selling a boxed copy unless you have the marketing budget of Activision/EA/THQ/Ubi. League of Legend's model is the best possible one to emulate.
Also, zfz vs. Tao last night is going to be edited as well as a post game interview with yours truly, and will be put up on NASL.tv in the next week as a promotional game for T:A as an E-Sport. Very exciting times.