B/c the LEDs require a driver which runs on DC [the better case is constant driven], the space constraints are too high and there is not enough room for heat dissipation which in the US kills the driver (as running on 110/120AC is less efficient), and in Europe it tends to kill the LEDs because they get to be overdriven, but the driver dissipates less heat. The power factor on all them tends to be atrocious, usually 0.5phi. They tend to quite noisy, esp. when it comes to EMF. In short there is not enough space to have a decent LED driver along with enough space for heat dissipation for the LEDs (usually only 15%, being generous, of the energy will be emitted as light. The rest is heat, so if you see 8W of LED, more than 6.5W is just heat)

Pretty much almost all LEDs you can buy in a retrofit case are almost guaranteed to be overdirven to show better numbers and be 'brighter'. Near ceiling larger fixtures can be designed for LEDs. They tend to have an actual 15-30k hours lifespan.

Dimming the LEDs is the next atrocity, esp. when it comes to chopping the sine wave. The LED dirvers have to work with the chopped sine wave and detect how much it has been chopped to reduce the current or the PWM.

About the AA(A) and the TV. I can control the TV w/ bluetooth and an app but I find that incovenient. However NiMH nominal voltage is 1.2V which fits the 1.5 of the alkaline batteries. It's good enough already. So yes, it takes different chemistry unless the remote controls provide built-in step-up/step-down converters, effectively variable operational voltage.