Much less fear of it getting stolen/stripped. I use my beater bike for errands around town and whenever I have to park it to a parking meter in urban areas.

I would hesitate to park a $1000+ bike outdoors unattended for over 2 hours in an urban area.

If I could easily and safely store my bike in my office, I'd definitely ride the nicest bike that I could for my commute. But even so, it's nice to have a beater if you live within 3-5 miles of a lot of places that you frequent a lot.