The problem is it is not as strong as the other summons. The summon pathing and AI is gimicky and special moves hardly hit, compared to the absolute consistent constant pressure a snake offers.
Compare likely scenarios where a summon wouldn't be kited easily:
Scenario 1: A medic reviving
Snake vs Panda - snake will make it impossible to rev the player because in the 10 seconds it can do 1300 damage. Panda may stun and cancel the rev yes (on a very high RNG chance), but the snake will literally make it impossible and kill the medic.
Scenario 2: Fighting 2v1 in the DZ
Snake vs Panda/Dog/Weasel - dealing with 2 players + a summon is hard enough, but you can invest one full combo to deal with the summon at not much chakra cost, and then fight a very difficult situation (2v1). Vs a snake, you will not kill it in 1 combo, and dealing with it becomes impossible and it's doing 99 damage per attack, you cannot stand still to charge even if you get less pressure from the 2 players. A 2v1 + dog/weasel/panda is very difficult. A 2v1 + snake is impossible.