[hakfoo]

There's a reasonable case that Private Browsing and Tor serve different enough use cases that they're not interchangeable.

Private Browsing: The goal is to prevent embarrassment. I'm looking at porn or shopping for gifts for my spouse, and I don't want it showing up in the autocomplete/history/remarketing ads as much as possible.

Tor: The goal is to prevent imprisonment. I'm accessing stuff that's politically sensitive and either inaccessible or likely to trigger consequences if it's detected by local ISP infrastructure.

Obviously, Tor offers a higher overall security profile, but tends to break things (services using IP blacklists, services that don't do well with its performance characteristics, etc.) that people expect to work with today's Private Browsing.

ISTR when one implementation of it came out (not sure if it was Firefox's or the original Chrome Incongito mode) the launch page said point blank "this will not hide your movements from your ISP, governments, site hosts, etc."