[CSS3] General question about CSS3 vendor prefixes

Why are vendor prefixes necessary? Why can't the various companies that
produce these technology funnels just support the attributes as they are
written in the CSS Style Attributes Candidate Recommendation? Why is it
necessary to use different attributes then everyone else? I cannot
understand why they cannot provide additional support on each attribute with
each consecutive release and just use the standards compliant attributes.
These attributes force web developers to either not advertise standards
compliance (losing business), use images (takes much longer to load, also
losing business), or make a less aesthetically pleasing website (losing
business). I understand that this ability to specify vendor prefixes is
allowed for, but then either the vendor specific attributes should be made
valid (probably not a good idea), or remove the allowance for vendor
specific prefixes.

Thanks for clarification,
Mark Ayers
a.k.a. markthema3