Are memory leaks only caused by Instances and higher scoped variables?

I know that the following will cause a memory leak (included fix):

--Part never gets garbage collected
do
    local p = Instance.new('Part')
    local dataTable = {Message = "Test"; Part = p}
    p.Touched:connect(function() print(dataTable.message) end)
end


--FIX Part gets garbage collected
do 
    local p = Instance.new('Part')
    local dataTable = {Message = "Test"; Part = p}
    p.Touched:connect(function() print(dataTable.message) end)
    p.Destroy()
end

This will also cause a memory leak (included fix)

--The coinTable will store every player that has ever initiated this remote event on this server
local replicatedStorage = game:GetService("ReplicatedStorage")
local remoteEvent = replicatedStorage.RemoteEvent
local coinTable = {} --This is temporary and does not need to be saved in a datastore

local function addCoins(player)
    local coins = coinTable[player.UserId]
    if coins then
        coins = coins + 1
        coinTable[player.UserId] = coins
    else
        coinTable[player.UserId] = 1
        --started at 1 to simulate adding a coin
    end
    for i,v in pairs(coinTable) do
        print(i, v)
    end
end

remoteEvent.OnServerEvent:Connect(addCoins)


--FIX adding this will clean up the table entry
players.PlayerRemoving:Connect(function(player)
    coinsTable[player.UserId] = nil
end)

Is there anything else I'm missing that could cause a memory leak? I don't use temporary scripts and have little to no instances. If my events are permanent as well as my functions, am I good to go? Thank you