Tridents use the same parameter than arrows for despawn rate.

The problem is trident are rare items and arrow despawn rate is often set to a low value in lot of servers to reduce lags (for example, in the optimization guide lowering the value is a recommandation).

So, if you set a low value, players haven't time to get it back which could make them angry.

Tested on:

• CraftBukkit version git-Spigot-56f8471-6567017 (MC: 1.14.4) (Implementing API version 1.14.4-R0.1-SNAPSHOT)
• CraftBukkit version git-Spigot-530f668-de42aa1 (MC: 1.15) (Implementing API version 1.15-R0.1-SNAPSHOT)

How to reproduce:

1. Change world-settings.default.arrow-despawn-rate in spigot.yml,
   to a low value (for example 20 to be sure to view the result quickly)
2. Launch the server
3. Get a trident
4. Launch it to the ground / a block
5. DO NOT pass on it with your player
6. The trident will despawn quickly (depends on step 1).

What could be better:
Have a distinct parameter for arrows and tridents, like paper does with "non-player-arrow-despawn-rate" and "creative-arrow-despawn-rate".