tl;dr Plug-in solar inverters must power off within a second if they stop detecting the grid's sine wave.

Generators have no such protection and will happily backfeed through the transformer outside your house to energize power lines. Line workers are careful, but there have been deaths. After hurricanes seems the most common based on a quick search.

So it's not a stupid question, indeed you should never plug a generator into an outlet. The double-ended "suicide cord" which allows you to do that has that name for a reason. (It can be fine to plug a generator into an inlet circuit, if the electrical panel has a proper interlock that physically forces disconnect from the utility before connecting the generator inlet.)