Bad memories. I particularly enjoyed fighting with third-party programs that installed system cronjobs in the various tabs, and having to remember to go and find them after package upgrades and try to figure out how to robustly identify when their processes were running so my other cronjobs wouldn't overload or clobber state, since the third-party-installed jobs didn't play along with any lockfile-based coordination we used. Wants/WantedBy/Requires are godsends by comparison.