To me it seems more that people are operating under the assumption that a score will either be at it's maximum possible value, or it will be 10 or less - so they just don't think that any character would have a +2 dexterity modifier.I often feel that people hate on medium armour due to wanting to boost Strength or Dexterity with no points in the other one.
I think this. Also I miss the move penalties imposed by heavier armour.To me it seems more that people are operating under the assumption that a score will either be at it's maximum possible value, or it will be 10 or less - so they just don't think that any character would have a +2 dexterity modifier.
Most heavy armors do have move penalties, assuming the players involved aren't outright refusing to use heavy armor on characters that don't meet the strength requirement to avoid them (a cleric in one of my campaigns wears heavy armor because he doesn't have a great dex, and suffers movement penalty because he also doesn't have a great strength, but he still wants the best AC he can manage so he wouldn't dream of downgrading to medium or light armor).Also I miss the move penalties imposed by heavier armour.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.