To be honest, ALLFORHIM, I’m not entirely sure, but this would be my thinking:
The worship is observing, respecting, and assisting (Through prayers that the offering will be acceptable, which we say at every mass, ((Not to be confused with actually bringing about the transubstantiation, only the Priest can do that))) the sacrafice. Recieving the Eucharist is not the same as actually worshiping. It’s a sacrament, which is a little different.
The other reason we are not required to recieve as often as every Sunday is in case the parishoner has mortal sin on his concsience, in which case he can’t recieve that week. The requirement is to keep Catholics still recieving, without requireing they recieve every week.
I’m not sure I’m explaining myself very well.

Do you sort of see what I’m saying? To be a practicing Catholic you must do these things, but the Church doesn’t want to micromanage your relationship with Christ (but they do want to make sure you at least do, and know, the bare minimum).