You're not entirely wrong; ultimately if they put enough resources towards it they can probably catch quite a number of people. But governments have limited resources and really don't track everyone all the time. Not even in 2026 are they able to do that yet. It helps if you maintain some level of opsec. If they really want to get you, they can get close, but see eg Ed Snowden; who managed to stay ahead of the US government just long enough to reach relative safety (FSVO).