LTC or other altcoins are just a way to make some money.
They are not really useful at all.
Your words perfectly describe what I don't understand after 6+ hours of research. Why is BTC more useful than LTC?
Because more people use it (search for network effect).
Litecoin is a copy of Bitcoin with only a few changes and came out after Bitcoin, it doesn't offer any big advantage.
In theory Litecoins could be just as useful as Bitcoins, but there are only few reasons to migrate to them.