virtualenv solved conflicting dependencies but pip is what made installing & managing them convenient. I see many people who use pip without virtualenvs.

True, in my limited experience venv and pip goes hand in hand. But I can see use cases where you use them apart, more so with pip then venv.

Initial pip release was also 2011. Now I wonder what I used pre-pip?!

edit: easy_install, doh!

Yeah easy_install, which theoretically worked (kinda), but alongside pip there was also the overall pypa effort (both marketing and technical) to make the whole thing work e.g. update or even fork the more abstruse projects such that they could actually be installed via pip. IIRC that was the primary reason for Pillow forking PIL.