Nobody can use the "/plugins" command, even with the "bukkit.command.plugins" explicitly assigned (not even with " * " or opped by "/op "). From console, it can be used with no problems though.
Using spigot-essentials, as expected, everyone can use it by default.

What permission plugin are you using?

Oh sorry, my bad, i forgot to check back. It was a conflict between GroupManager and PermissionsEx. I'll close it since I was using GroupManager on top of PEX which is not something anyone should do.