A pallatal expender is only good for people who have a crossbite of their back teeth. It only expends the upper not the lower, it has to be done early when the child is still growing, after that the bones fuse and an expander will just push the teeth sideways and not expand the bones. The lower cannot be expanded without surgery. When the child stops growing the upper also cannot be expanded without surgery. I am a dentist, I have a pretty good understanding of these things. Your orthodontist would have an even better understanding of these things. The people on here only know what happened in their one specific case, generally there understanding of what was done, and what the problem was that caused it to be done is extremely simplistic. It is best to not take treatment advice from a person with such knowledge as every case is different and only someone with training will know how and why to treat a certain individual.
Pulling teeth isn't a last resort at all. Crowding of teeth is because there is a tooth size to jaw size mismatch. If the jaw size is normal and the teeth are big it depends on a variety of other factors. If the crowing is minimal they may slenderize the teeth a tiny bit to create room (a couple millimetres at most), or they may flare the teeth slightly to expand the arch (if they are tipped inwards in the first place). If there is a lot of crowing, or if the teeth are already flared outwards, the only option is to remove teeth. Expanders make the arch bigger also, this can allow for more space to accommodate larger teeth as well. But only if the upper arch is constricted in the first place (which results in a crossbite of the back teeth). If the upper and lower are in a normal bite, and the upper is constricted that means the lower is constricted also so the palate can't be expanded without surgery to the lower jaw or else the upper teeth would jump past the bite of the lowers! Luckily this is very rare, the lower jaw generally forms normally, the upper jaw often becomes constricted after birth as a result of thumb sucking but the effect of the lower jaw from thumb sucking isn't to constrict it, its to prevent it from growing forwards at a normal rate which leads to people who have a retruded lower jaw (the opposite of what Jay Leno has)