You're forgetting that LimeWire is not the only program on the network, there are others as well, and many of them do have that option. Also there have been development editions or forks of LimeWire in the wild that had that option. Perhaps two more things you should know: the browse host feature has been buggy in the past when LimeWire would send a malformed request packet so e.g. no results would be returned, and turning it off in some situatations cannot guarantee that no filelists are sent over the network, since if you connect to an ultrapeer, your filelist are sent anyway.