If you arent using a character, it does make sense not to activate it. If you luck out and pull a full character from a data pack, the character will fully unlock and you will keep all the shards you currently have. If you spend your shards to activate and tehn pull the character, you only get half the unlock cost rather than the full character.
For example, I'm at 88/80 shards for Old Daka. If I pull her I will have a full Old Daka plus 88 shards. If I unlock her now and then pull her, I will be at a full 4* Daka but with only ~48 shards.
