With very few exceptions (such as JL's introduction of its Skywider Y seating on some routes - which I was quite happy with on a recent trip), the trend is towards narrower seats and reduced legroom as the airlines cram us in tighter.

I'm only 5'8" tall and average build, but the narrower width is annoying, I imagine even more so for anyone with a wider frame. I can get by with less legroom (within reason) - though I'd obviously prefer more - but the width can be quite bothersome when you're literally rubbing elbows with your neighbor. When I travel with my wife it helps slightly since we can obviously stand to be touching, but on a long-haul flight even the happiest couple needs some personal space!

Packing more seats across also makes the aisles narrower which is another annoyance when getting up and about during flight. And altogether it just creates a less comfortable feeling psychologically.