While it is certainly true having active thermal activity is considered important for a planet to support life, and radioactivity in the core allows large planets to keep it longer, just having it proves nothing. Distance from the Sun and atmospheric composition are probably more important. Or is that not your point?
Goa, I believe you are correct that distance from the sun (i.e. any host star) and atmospheric conditions (like having just the right amount of greenhouse effect) are the most important determinants of surface temperature, and life certainly depends on that.
I haven't stolen information from another site or article looked it up but I don't think we get much direct heat from our own core (I assume b/c the thickness of our crust?). Decay of radioactive elements only produces heat inside our planet , but it also helps create the magnetic field that protects our life from harmful solar radiation (the really high energy rays that could mess with our molecules). Friction and left-over heat from Earth's formation also contribute to heat inside.
Ryat, this came up because Mecha-Lenin suggested Strip-to-the-Core only work on terran and desert planets as a balancing feature and that a nerdy-lore reason might be needed. I don't think he was serious but I made one up anyway.
So I figured that terran and desert planets would be larger than asteroids and dwarf planets and that they would be more likely to have cores that were still radioactive and molten (planet age is still a huge determinant).
To leave out Ice and volcanic planets, i threw in a bit about the titan ability requiring a certain metal-crystal ratio so a planet with mostly one or the other wouldn't work. I realize that it's the planet's asteroids that are mined in-game but I assumed that the planet would have a similar composition to nearby asteroids if they were created in the same proto-planetary disk (maybe crystals can't form under too much radiation so they have to be around cold planets?).
(Speaking of which, I'm not sure the bolts of energy(?) that Advent Disciples and TEC Cobalts shoot can be considered lazers; i I haven't run the numbers but it looks like they are traveling less than the speed of light in-game, the Kol's and Ilum's beam weapons look more like lazers. Completely different subject though.)