node_delete and caching
One reason i see is Entity Reference...

For Example -


A block which lists some nodes part of your delete list.
A node which has entity reference to your deleted node
A view page which has some of your deleted nodes


Reason for clearing all the caches: When a node is created/updated/deleted there can be many pages in the site which are dependent on the current node in question. It is next to impossible/very difficult identify all the dependencies and clear the caches only for those pages. For this particular reason, to make sure that no stale data is served to the end user drupal by default clears all the caches.

So, It makes sense to Clear the page and block and node_load_multiple caches as documented in node_delete_multiple function.