What’s the problem with that? The voltage of lithium battery is between 4.2 (shortly without load at full capacity) to about 3.4-3.5V with no load at low capacity. (A load can lower significantly the voltage across the battery)
Because the battery are 3.6-3.7V on average you think you cannot power thing that need a higher voltage?
Then how do you apply the 10-20 kV needed on a CRT screen from your main 110-240V?
There are plenty of way to make higher voltage either in DC or AC, and I’m pretty sure theare are LCD panel that can work at 3.3V or 1.8V.
Maybe you are talking about the backlight? Well even with the two cell in series (which is the most likely scenario) you have just 7.2V on average which may not be enough depends on how the LEDs for the backlight are connected. It is more than likely that there is a step up voltage regulator for the backlight, either on the main PCB or on the LCD panel itself.
So I’m not sure what is the problem?