Obito is a bit hax because of all his modifications, Madara and Sasuke are transmigrants with atypical chakra reserves and EMS which averts the usual chakra/usage restrictions, using Mangekyo did drain Itachi in spite of his prowess, and aside from these guys, most Uchihas didn't even achieve Mangekyo.
So you're left with the regular Sharingan, which they could choose to activate at will, which meant it wasn't draining their chakra except when they chose to use it in battle
Therefore, the average Uchiha wasn't walking around with an always-active EMS, they were walking around with regular eyes. In battle, they'd probably be employing 3Ts at best. 3T usage is tiring for like, novices and non-Uchiha, but its very negligible for dudes like Itachi who have mastered its use and can use it perpetually, or within the context of momentary battles for the common Uchiha mooks.
In conclusion, the premise of OP is flawed. The Uchihas having Sharingan is not sufficient proof to say they were burning significantly more chakra than the Senjus, nor that they required larger chakra pools to use it efficiently.