Can some wheel expert help me-

I went to Costco to get the wheels balanced and rotated on my 2000 TL. He said that he cannot rotate them because front tires are bad and I need to get alignment checked. Visually the tires/treads look ok. Is this a common issue and what causes it? What is the best next step?

 

bad alignment and possible bad camber, take it somewhere that does alignments and they will fix both. Why costco?

 

You say they look ok, and they say they are bad. Did you ask them to show you where they looked bad? If they say you need an alignment due to wear maybe you do. Have an alignment shop or them (if they do it) check and fix the alignment.