Why all the angst about reclining seats? Surely if you recline your seat the person behind you reclines theirs and that person then has the same amount of space as before
Not all seats can recline - often the very back row of a cabin can't recline. You don't always know this when booking though or you are just allocated a seat at check in.
A reclined seat in front of you makes it difficult to use the table to do things such as crosswords, puzzles, colouring etc. You can't lean over the table as the front chair is in the way. Hence why they should, at the very least, be raised for meal times.
It often depends on how a seat reclines. The one I was on this morning, when you reclined the back moved but also the seat moved forward too - so you reduce your own legroom slightly but have less leg room impact on the space behind you. This was a much better system. Although, I was surprised - no one in our section of the plane reclined last night (7 hour flight) Everyone just slept sat up.
Some seats however, just the back reclines including quite low. If you've long legs do your knees are already touching the back of a seat then recline makes this much worse, even if you recline your own.
A reclined seat makes getting in and out of the seat, such as standing to stretch your legs, go to the toilet or going to get some water more difficult. It's impossible to do from the window or middle seat without knocking the back of the reclined seat often.