He is just your fwb, there is no reason he should text you every day.

If that's something you want, maybe you like him as more than an FWB?

Or if you don't, it's JUST as important to set expectations in a FWB situation as it is in a relationship. Maybe if you guys talk about it you can find a compromise. But generally, texting every day/constantly is not standard in a FWB situation.