It depends on the character build. Some builds will level up very fast and in a number of different areas. Which will in turn lead to a weak character. While we know that the curve eventually breaks, you still have to get to that point. Although I think the most compelling reason for getting str up's is to carry stuff rather than anything to do with combat.
My new character levels so slowly that +5's are pretty much a given (when wearing heavy armour and using a weapon of some sort).
Although it's finding stuff like dwarven at level 6 and silver at level 2 (as well as a +15 damage stone) that has made life very easy, rather than the stats.