Hi Nicknick,
Yes, you're right: it can save a lot of money if you repair your weapons and armor on you own

On the other hand: money isn't a problem (maybe only in the first beginning) at all in DD.
So for me it is just a pure personal thing to choose for these Skills (Repair and Identify).
Most of the time I choose first 1 point (or 2 points) in Identify so I can identify the most of equipment I can wear directly ... Later on I go for maximum 1 point in Repair (except if I find an equipment with +1 to Repair early in the game).
Mostly I find it fun to do things on my own (repair, identify, making potions...)