You did really experienced paying 10-15 USD for a single transaction with $5- $50 input? Personally I never experienced that one.
AFAIK, the transaction fee is relative to the traffic on the mempool. The higher the congestion is, the higher the fee will become. I'm not really so sure, but that's what I think the reason behind it.
People are paying higher too become more priority on the mempool. Racing to be accepted first.
I guess a lot of traders won't hesitate to make their deposits whenever there's a spike in price like what's been happening in the last few months. I also paid $10 a couple of times this year it was the worst time to make a transaction because of the price, difficulty change and at the same time the hashrate going down made the situation even worse.
Fees should be reduced. Higher fees discourage new investors.
Reducing the fees would require everyone to use the same amount of fees and it's unlikely to happen.