In addition to factors others have mentioned you can end up with unexpected interactions with folks in row 6 behind you. I don't generally recline in F but the last time I was in row 4 (with no hard bulkhead behind me, as I soon found out) I was tired and decided to try reclining. Normally it would be polite to look behind me before reclining and perhaps even warn the person behind me but of course I couldn't see. I assumed that because I was in the last row of F I wouldn't be bothering anyone but I was wrong. As soon as I reclined the guy behind me yelped and loudly complained about me taking his space. I was surprised but put my seat back up. Then during the rest of the flight the guy seemed to be constantly putting things in and taking things out of the pocket on the back of my seat. He did it roughly enough that it was very noticeable, much more so than what I would consider to be normal.

So this is one more reason for me to avoid row 4.

Edited to add: I think the fact that the curtains kept us from seeing one another made it easier for this situation to occur. I decided I'd rather be able to easily see the people behind me if there was a chance of this type of interaction.