Since when the design specification from the manufacturer is any important ? No matter they did not put cooling, i will put, as i don`t want to worry about the temperatures, no matter how tough the old hardware is.
For example 3Dfx cards early ones does not have even heatsink, but they are stoves, not to speak about the Voodoo 3 and Voodoo 5 they are all heaters, but as you state the manufacturer did engineered the whole thing, so we don`t need to check the temperatures, we will be just like the normal user that does not have a clue what is it is in the PC case and we will play it simple. For example i check on all my components that im using the temperature, and if is warm under stress/load it is ok for me, but if some parts are heaters under idle, then there is big problem, and it need some upgrade...
Also all manufacturers are cheaping out even on way more important things like japan caps, VRM elements, transistors, chokes and other, and you are thinking they will not cheap on the cooling really, as they cheap on that alll the time they can, to reduce cost and saving money.... That does not mean, the computer some OEM did make will fail, no it will work, but instead of working one more cool environment it will work in way wors one, that will reduce lifespan, will even cause some day the components just to die from heating up....
In the end i will cool my stuff, while you can use yours as heaters, after all it is winter in EU, so maybe you don`t need cooling, no matter the temperatures...
Mah systems retro, old, newer (Radical stuff)
W3680 4.5/ GA-x58 UD7/ R9 280x
K7 2.6/ NF7-S/ HD3850
IBM x2 P3 933/ GA-6VXD7/ Voodoo V 5.5K
Cmq P2 450/ GA-BX2000/ V2 SLI
IBM PC365
Cmq DeskPRO 486/33
IBM PS/2 Model 56
SPS IntelleXT 8088