Its more of a show-off card than a plug-and-play Pokemon for your decks
However, since its a Pokemon from the original 151, it will command higher prices than later Pokemon, even in more recent card sets.
I know that there are some seriously evil lands in Legacy and Modern (Dark Depths, Wasteland, Valakut, the Molten Pinnacle, Celestial Colonnade, Eldrazi Temple and, of course, Tron), but youre losing card advantage while also giving your opponent a free rainbow land
With so many sets in Pioneer, the chance that the energy core is just the best way to build decks to such an oppressive extent is much less likely than it was in Standard because ultimately there are still only two sets that contain these energy cards
Hoping to add some valuable chase cards to your collection
It made it easy to pay for the surge cost, and give enough stat boosts to take life totals down to zero since your opponent likely didn't have many creatures to block with