Flying at higher altitudes in lower density air also reduces lift, though [1]. A plane does get extra benefit from flying higher as drag on the fuselage is reduced, but there is a limit — the plane has to go faster to make up for the reduction in lift due to the reduction in air density. An electric plane ends up being able to fly a little higher, but not by much. See these notebooks for details:

https://github.com/gusgordon/atmosat/blob/master/atmosat.ipy...

https://github.com/gusgordon/electric_jet/blob/master/plane....

[1]: https://en.wikipedia.org/wiki/Lift_(force)#Lift_coefficient