They're a blight on the already tight, difficult, and crowded streets of Boston. If you're traveling down Tremont St in the South End, for example, just give up on trying to use the right lane for travel. There'll be multiple ubers/lyfts suddenly stopping for long periods of time on every block.

Cities need to designate pick-up/drop-off spots away from heavily-trafficked streets for these pseudo-taxi services, UX be damned.