Well that was before I found out you could feed the squirrel card reveals. When you first start out(In my case) you'd want card reveals to make it easier on yourself. You get a few guaranteed SR gacha tickets, so obviously having a card reveal would make it safer for you with not wasting something like that. You're right though, once you get into the mood of guessing right and SRs aren't that vital to your SED at the time and new, then the card reveals aren't that useful since you're ultimately gambling for two things with or without reveals: is the SR new, and is it even in the gacha if not guaranteed?

Also it's about the rarity, I'm lvl 31 right now, and if I remember correctly I only received 2 card reveals in the missions, the least amount of any reward in the missions right now (I think the next one was the liquor you use for the squirrel) so just having it feels good I guess?

For players like you and I, you're right it's mostly used for feeding the squirrel. There's a rare chance you could use it for event gachas and normal gachas to finish your collection. But later on when new cards came out, if you believed that there was a SR in a gacha that you haven't received yet, there's an event card or limited card that you won't get in the rankings like Runa but can get in the gacha, and your luck is poor, wouldn't having at least one be a little safe?