Because paying X is part of the normal casting cost, paying an alternative cost for these cards will result in X=0 unless the alternative cost itself specifies a value for X, such as Lantern Flare or Disrupting Shoal
One of Pokemon's biggest collab is that with Build-A-Bear Workshop
Some are creatures with triggered abilities that you may want to time more strategically
(Although I did have a bunch of Shadowless cards) As you said, there may have been a select few places where this was an exception, but I think peoples view of just how common 1st ed Base cards are is heavily distorted because of the prominence of 1st ed Base in the high-end collecting world
Irony: In a dialogue, Ramza and Delita discuss the sincerity of the latter's affection for Ovelia, at which point Delita claims that he would give his life for her
4Kids Entertainment to Transition Its Representation of Pokemon" (Press release)