Centerfielders always cover, they're just never in frame because it's dangerous to get too close to the bag in the event the ball doesn't go straight to them.
and 3rd base is an even more dangerous position to back up the throws.
They do it, but the sidelines sometimes jut into the field at weird angles so if a throw bounces off a sidewall, the ball goes toward center or SS. So it's tricky to begin with.
Also, I thought you were Dominican.
The fact that you're even asking these questions makes me think that you aren't.