Our single tuners can take the power from 5V which requires a higher current of course and warms up the components more than with 12V.
However if the 12V power supply is plugged in less current is required and the tuner will be cooler (and we deliver our tuners with a 12V powersupply by default).
- higher voltage - less current -> lower temperature
- lower voltage - more current -> higher temperature
Certainly this depends how much power your LNB draws, a single LNB might be no problem with a 5V power supply via USB, while a quad LNB definitely needs a power supply.
There are some niche projects which are perfectly fine even without LNB powersupply since the lnbs or data source is powered elsewhere.
If you plug in the tuners to a signal generator of course no power supply for the LNB components is needed at all.
For cost saving only allowing a 5V power supply doesn't make any sense (but yes there are some ..)
PC systems also provide 5v and 12v ports, actually the 12V port could be used with an adapter with our tuners too of course.