Then the cost of stamina abilities will probably go up to balance it out. So do you really want it?
Why would it go up?
Mag skill costs aren't balanced around magicka steal, they are balanced around the 20% additional stat pool they have.
If there was minor stamina steal, stam players would pretty much have infinite sustain. See all the above comments about stamina abilities being much less, and the fact that you get a free full strength weapon enchantment (which can be absorb stamina) when using DW/Bow versus double staves.