It is awful - I'm glad you never had to deal with. It provides little revenue and causes a huge amount of hassle and makes living overseas way more difficult.
1 - just trying to work through what all might possibly be owed and not owed to US as well as the country(ies) one operates in.
2 - Identifying through which paperwork to declare it, while also ensuring income / business reporting is copacetic with the tax regime of the country that same is actually earned in. As a business owner, (many operating overseas are looking after a business) I have to complete corporate accounts (which costs $$$$ and takes forever) before I can file American income tax for the same accounting year.
3 - the value of the tax liability itself is a distant third in terms of hassle than any of the above. (I’ll include in this bucket the fact that Americans are taxed on income earned abroad, putting us at enormous disadvantage for work opportunities vis—a-vis peer expats who come from other countries)
For this change to occur, many senators and representatives would have to be directly and personally incentivized to make the change.
They aren't.