The hard-link strategy still saves disk space — although not as much (see other replies and discussion).
Possible reasons not to symlink that I can think of:
* stack traces in uncaught exceptions might be wonky (I haven't tried it)
* it presumably adds a tiny hit to imports from Python, but I find it hard to imagine anyone caring
* with the hard-linking strategy, you can purge the cache (perhaps accidentally?) without affecting existing environments
The hard-link strategy still saves disk space — although not as much (see other replies and discussion).
Possible reasons not to symlink that I can think of:
* stack traces in uncaught exceptions might be wonky (I haven't tried it)
* it presumably adds a tiny hit to imports from Python, but I find it hard to imagine anyone caring
* with the hard-linking strategy, you can purge the cache (perhaps accidentally?) without affecting existing environments