Please note that number is in USD.
I personally have no problem staying under $100k; I live in Germany and work at a university. But imagine if you lived in Switzerland or Norway. Somewhere with a high cost of living and with a currency that is very strong vs the USD. Then it doesn't take much to go over that 100k.
And even though I don't have to pay US federal taxes (being under that $100k), I still have have the file state taxes, federal taxes, and an FBAR. Every single year. The time and effort is an annoyance, but what bothers me most is the principal. I don't live in the US; I don't use its services; and still, every year, I have to allocate a weekend to provide them with every single detail of my financial life.
---Alex