Yes you do.
And you miss enemies because you don't exist in a power vacuum.
In other words, as you go up in BAB and STR, the enemies go up in AC - be it natural armor or a high dex, whatever. Even if they don't, they also get access to magic spells, items, potions, and scrolls. Basically, monsters have the same resources the players do, which helps keep it interesting.
Truth be told, though, if you are into optimization at all, you shouldn't ever have issues hitting a monster. While by RAW you can't stack more than one item with a STR bonus, you can get class features or feats that increase your modifiers to attack. One of my favorites - a 1 level dip in Shiba Protector gets you your WIS to attacks and damages. You might find http://www.giantitp.com/forums/showthread.php?t=125732
helprul to see how to get what stat to what ability - the first post is sorted by stat, the second is sorted by what you want to boost.