The IPMI chipset also costs some extra money, consumes a non-trivial amount of power and generates a non-trivial amount of heat given the application. If you want all that, it's already available, but not at this price & form factor.
sure everything have cost
for simple low end baremetal of fireware/router, simple/desktop mini-itx or macro-atx is very good pick since running 24/7, without a major issue.
if you are talking about filer server or important "thing" server or something 24/7 remotable , yeah IPMI is the first priority.
on my some systems, ipmi pools 5-10W for sure. this is reasonable due on monitoring and add sensors.
if you factor low-end power intel 10W rated or less, consumption is trivial.
I just throws some thoughts that desktop mini or micro atx with low power cpu is a good candidate for low end baremetal or firewall/router, Need to ad extra Intel Nic too (add $10 for a used dual 1G ethernet).
honestly, my first build server was desktop AMD Athlon and pentium 4
and move to dell T series pentum 4 and AMD socket F. I am moving back and forward to adjust my needs and save $$$
once again, I totaly agree that IPMI is important for trivial server or for people whom is lazy/prefer remote access 99%.