Given the company, it's usually long-term contracts that more closely resemble full-time employment. The location is also usually outside of the biggest, most expensive cities.
$120/hr * 40 hrs/wk * 50 wks/yr = $240K before self-employment taxes and paying for insurance. Ends up being comparable to typical compensation in cities that aren't SF, Seattle, or other top-tier markets.
Now if someone was doing more typical ad-hoc freelance work on a project basis, $120/hr might be too low for typical work. However, $90-120/hr as a contractor with a long-term contract and stable pay over 12-18 months is not uncommon.
Unless someone has a lot of new, small contracts knocking at their door nonstop, it can make more financial sense to take a $120/hr long-term contract over sporadic $200+/hr work that changes month to month.