[SAI_Peregrinus]

Haven't you? There's quite a bit of closed-source software based on permissively-licensed code. You can get the upstream source for the permissively-licensed code, but not the modifications made to it. Windows (used to) use some BSD-licensed code for a few network utilities like nslookup.

[engeljohnb]

I guess I considered that completely separate from open source. For instance, I've heard that MacOS is "based on BSD," but since MacOS itself is obviously not open source, it's not an example of open source software that doesn't provide the Four Freedoms.

[SAI_Peregrinus]

Open-source software provides the four freedoms, but doesn't necessarily require preserving them transitively.

GPL software requires preserving them transitively and requires derivative works using the licensed software as a component to provide them.

MPL requires preserving them transitively.

BSD/Apache/MIT don't require preserving them, but still require the resulting software to include the original license & attribution. In the case of a closed-source program distributing (say) MIT-licensed software with proprietary modifications, the resulting binary is still released partly under the MIT license & includes the MIT license text, but doesn't include the source code.