Because of the resources you have to manage.
In HF all you had to manage was your spacing and health.
Than ST added a super meter and some people hated it.
Than Alpha added guard meter, super meter etc
Third strike is just based around conserving your super for big damage.
And now in SF4 we have health, grey health, ex meter, super meter, and ultra meter.
As well as marvel 3 with Super meter, assists, red health, and x factor.
So I think that the difference between all of the old FG’s of the SF2 days and now are the resources you have to manage in modern games. This makes the newer games be more akin to starcraft than street fighter.
My 2 cents.