why are aespa cards are mostly limited?

There are only three themes that aren't limited: Black Mamba, Lucid Dream, and There Can't Be Two. I've already collected the first two, but There Can't Be Two seems rare, even though it's not limited. Every time I purchase a yearly premium card, I get a different card instead of an Aespa card. And for the S card exchange theme, I have to wait for almost a month to get it. It's not like I can always log in to the game because I have other things to do outside of my phone. Now I've been thinking why mostly Aespa cards are limited and I'm too broke to buy them, and they're pricey too. Can Dalcom at least give us a new card that's easier to collect? T__T