Because at this point, as far as I can tell, this is still just baseless speculation. It could have been that, but it could have been aliens, we don’t have any actual evidence to base any of it on, hence it being easy to dismiss as a conspiracy theory.

Depend on how you look at thing as I recall:

• They were literally studying the different types of bat viruses
• They publish an article of similar covid like viruses and the similarities with HIV around October/November
• If I recall correctly the Lab was not categories to be allowed to work on such viruses

I think these three points are not baseless. Now we add other points:

• WHO were not allowed to do independent research, and I think UK and France criticized the report.
• US Intelligence suggested a few worker got sick before December, although it was Trump administration but Biden never released the full report.
• and I think in the note Fauci point out that 10 out of 12 don't believe it is natural. Although is not clear who they are but I assume they virologist at the time.

I think these are not baseless suggestions.