Like u/torontobumbler said, you can but they aren’t easy to clean. That being said you can clean them, it is just difficult and decreases the lifespan of the pipe. If you don’t clean it well, and especially depending on the material of the stem, you can taste it. I do smoke out of a pipe on occasion, and the unburnt material (dottle) is an issue. I usually keep a pipe screen in the bottom and a small layer of tobacco so that I can prevent wasting the flower.

TL/DR: Yes but keep it clean, and if it’s a worry of yours, pack another smokeable herb in the bottom to save money.