GAS Ethereum transactions can be expensive because Ethereum is also expensive, maybe this is a law of economics because the more expensive goods are, the more expensive taxes are too.
I mean, cryptocurrencies don't have taxes, but they do have something called transaction fees that allow the same thing as taxes. This is only my opinion !
The more expensive Ethereum is, the more expensive the transaction fees are seen from the decimal fraction of Ethereum, such as 0.00000011 gwei.