First, I'd point out that "SDE" no longer exists. The certifications are for
Enterprise Geodatabase Management, which is way more than ArcSDE.
Second, certification prerequisites include several years of professional
experience -- this is not something that even the most dedicated hobbyist
could achieve in under twenty years, so it cannot be effectively used as
justification to lobby Esri to give away server software.
Third, generous software evaluation programs already exist for software
evaluation by organizations (who would presumably have the means to
afford server-class technology), so I doubt those who make the decisions
on such things will be swayed to offer the same to individuals (who
presumably wouldn't).
- V