I noticed that in a restaurant with a few fish tanks (no Bettas.. just chcilids and angel fish and such) They were barely moving, and there was no light above their tanks.
Also, when Neon was in his 2.5 gallon tank he wasn't too active even though he had warm water and plenty of space. I add him to his 10 gallon with lights, and presto, he was super active zooming around everywhere. He is also more sluggish when the lights are off... I don't know if the transaction from small tank to large tank is what made him energetic, or the lights.... So, do you think a fish tank with lights makes a more active Betta? Just curious.