Why Do HVAC Equipment Makers NOT Date ALL Their Products?

Anyone looking at a resale house wants to know how old the heating equipment is.
And it seems to be a state secret.
I looked at a water heater today, and after going all over the data plate, all I know is that it apparently meets ANSI standards from 1994.
It is in a home built in 2002. That “1994” is not much help, as I assume they didn’t put an eight year old water heater in a new home.

Of course, the manufacture date is embedded in the serial number. And you can Google the serial number and manufacturer and generally deduce a production date.
But why so coy, fellows?

I like how Trane usually does it:

HVAC Label Photo

There’s your Date of Manufacture, at the top right of the data plate.
MFR DATE 2/2011
No mystery. No secret.
That unit was turned out in February, 2011.

Now, when was it installed? I dunno. Maybe in March, 2011? Or, June or July? But at least we know we can be assured it isn’t a 20 year old AC unit. And, it may have replaced one.
See, that home was built in 1969.