Witnesses should be recorded for every event, baptisms and marriage events included.
First, these witnesses are important people in the life of the person in question. Second, the witnesses' lives intertwine in at least this one way and possibly more. Third, research into the witnesses' lives may enable you to find out more about your person.
It's too bad most genealogy software does not encourage the recording of witnesses more than they do.
Note that early versions of GEDCOM had a WITN tag. This was removed in GEDCOM 5.4 in favor of the ASSO (association) tag with the RELA (relationship) subordinate tag which can do much more than the WITN tag could do. Not all programs support it fully and import or export it well. Some programs still support the WITN tag, and some have decided to use a _WITN user-defined tag once WITN was removed. So the sad result of this is that witness and relationship information does not transfer well between programs.