Crapware is especially worrisome because it falls into a gray area as far as security updates are concerned. Microsoft seems to deliver patches and updates for its trial software such as Works and Money through Microsoft Update, but each vendor takes a different approach. If the application only checks for updates when the user launches it, the user may have an exploit-filled older version that an attacker can still activate. If the application had a trial period that has expired, only some of the functionality may have been disabled and it may still be possible to exploit the code.
Even the security software that shipped with the system may contribute to the problem. You may recall that Symantec's antivirus software had a serious security problem a few years back. If Symantec's software was ever installed on a system, it often leaves behind running parts even after it's been uninstalled. I've pointed dozens of people to the Norton Removal tool over the past few years; could those zombie Symantec components provide an attack surface?
Removing crapware makes a system faster, improves system stability, and frees up space on the drive. To all those good reasons, you can add one more: improved security.