No, that isn't ok.

Several times I have purposely brought NO carry ons to ensure I had legroom. If United is going to push the "the area under your seat is your primary storage area" crap, then if someone wants to keep it clear because they have nothing, that should be their right.

It's like how I get yelled at now and again for only bringing a small backpack and putting it in the overhead. Fine, if you're gonna force me to stuff it under the seat, I'll just bring a roll aboard next time even though I don't have to (which I've started doing, btw. Sorry.)

I don't get FAs that are that lazy, and a little less so, I don't get flyers who still don't get if they book bulkhead they can't store things on the floor. But both are common.

No, that's not OK, And I would have at least expressed my discontent. In the end this kind of behavior makes it worse for FAs, since then people will do things to prevent it..