Why does Numbers crash when deleting multiple sheets from a table?

I think you may be mixed up on your terminology for Numbers:

are you deleting sheets (the tabs across the top)? or tables(the finite sized array of cells)?

I am assuming you mean tables since there is no way (I can see) to remove more than one sheet at a time. Assuming this is so... I cannot confirm your report that selecting multiple tables and they typing the delete key causes Numbers to crash.

I would perform a test on a new document and see if that is still the case. Also try the same test in a different user space