This is a known issue with these vans.
Located to the right of the headlight control dial is a thumb-wheel toggle switch that controls the operation of the interior lights. Normal operation has the switch set to the SECOND detent from the top of the switch, (the second dot above the dimmer area.) With this setting, all the interior lights, including liftgate and door-mounted ones will illuminate when any of the vehicle's doors are opened, or the remote keyless entry is toggled with the UNLOCK function.
If the switch is put to the top most setting, that turns the interior lights on in one fell-swoop without having to turn them all on manually. Speaking of which, the lights mounted in the center of the ceiling ARE NOT manually controllable. However, interior lights located above both sliding doors and 3rd row vent windows (if so equipped) will illuminate manually by pressing on them.
The ISSUE with these lights NOT coming on when doors are opened has to do with the thumb wheel switch itself. The two lights on either side of the overhead trip computer in my 1996 stopped coming on years ago, though all the other lights still do. For a while, I found if I jiggled the switch a bit, I could get the front lights to turn on when the door is open, but not so much anymore.
2000 Chrysler 300M [Daily Driver] 158,000 miles as of Nov. 2014
1996 Chrysler Town & Country LX [Always and forever the favorite.]
2000 Chrysler Town & Country Limited [Gone, but not forgotten.]