Super Mario 64/Headscratchers

Why does Bowser surround his levels with bombs?
 * In hopes that you really are a loser and will run straight into 'em
 * I assume that the "levels" aren't actually made by Bowser, but rather, he is simply making use of them, in an effort to protect the keys. The same question can be asked of why Bowser fights in places designed like the ones in the original Super Mario Bros, where he gets dunked into lava, with a similar answer - he didn't make those levels, he just utilised them.