>>33914758Because the Shroom of Succ is highly dependant on Sleep RNG.
If you fuck up the cycle, you can die pretty quick. This is why the Leftovers are important. It's not about a big SUCC, but rather a sneaky and patient SUCC. Let's say the Cycle was Hit>Spore>Sleep>Sub>Wake>Sub break>Leech Seed>Leftovers+SUCC> Opponent Attack. Your Shroom of Succ would be at 85-ish% health before the hit. If you don't die from the Attack, you can can reset the cycle and run the RNG again. With the Leftovers, it ensures survivability if you fuck up the cycle of SLEEP+SUB+SUCC.
However there are some interesting things that happen in the actual gameplay, the Sleep RNG never runs the same number of turns twice. So if an opponent was asleep for 2 turns, it'll go through a cycle of 3, 4, 5 turns (random) before resetting where 2, 3, 4, 5 are on the table again. However, in Pokemon Refresh, a Pokemon with an extremely high friendship rating can resist sleep, or even the incredibly rare instance of waking up the next turn!
The Shroom of Succ is a powerful tool, although its true power is limited to the same realm where Mega Fug flies freely, and where some general bullfuckery can occur.