Switching to monero would incur you, what? 0.1% fee total even when you add all the transaction fees? Doesn't seem like much of a problem.

The problem isn't just the transaction fees but markups by exchanges (BTC -> XMR, XMR -> BTC) that each take a cut. Last time I calculated this, even after shopping around for cheaper exchanges it was well over 1% in total fees and probably something closer to 3%, but I'll have to double-check.

I'm beginner, but if both ExchangeA and ExchangeB is investigated by law enforcement, ExA knows sent address and ExB knows received address. So it's not perfect unless you add intermediate private XMR wallet between A and B, isn't it?

Why would you buy BTC at all in this scenario? If you are going to an exchange you can just buy fiat-XMR and XMR-fiat.

Deposit money to Binance, covert to XMR, withdraw XMR is well under 0.1% total in fees.

I wouldn't. As you mentioned, I would just find an exchange that supports fiat <-> XMR. I'm just responding to the top-level comment that specifically referred to Bitcoin as the preferred currency for these transactions.

Sure, at small scale, not much of a problem. But start moving $$millions, and you'll simultaneously move the market, paying more as you buy and receiving less as you sell.

There is no such thing as a free lunch.