My daughters baby teeth are crowded. Ortho wants 4 pulled but did not recommend an expander just braces phase 1. Why? Won't her adult teeth crowd?

Interesting. Usually when baby teeth are crowded the jaws are too small for all of the permanent teeth also. Removing certain baby teeth can allow front teeth to unravel so crowding is transferred to the back. Sometimes the crowding is so severe that arch development (expansion) can't overcome the amount of crowding. Your orthodontist has measured tooth size vrs space available. Ask for an explanation.
Get a 2nd opinion. I have always found that in ortho you can have as many treatment recommendations as you have orthodontists. If this one's opinion doesn't sit well with you, go see another. If 3 or 4 orthodontists all say the same thing, go with it!
Braces retain. Not uncommon for treatment of crowding to have some primary teeth removed to allow permanent teeth more room. Lower and upper front teeth may not have the space to erupt in correct position and start to overlap, a narrow arch. Often the cuspids are extracted to provide more space since these teeth don't come in till much later. The ortho then places braces to align teeth, and preserve space.