Here in Switzerland if you don't give proof of insurance the state will pick one for you. Then if you don't pay, it's like with any other bill, you'll get into troubles really quick.

Its send to collections. So you're only fine if you are poor enough to not have anything they can take from you. And at that point you are eligible for gov support to your healthcare bill anyway.

Here in germany you can actually kind of get away with not paying for a while when not consuming. But coverage has to be continuous, so if you need insurance since you want to go to the doctor a few years down the line, you have to pay up for the entire period.

There's always stragglers, hold outs, conscientious objectors, cheats, freeloaders, randos, or whatever.

Just think of them as "overhead".

Spend a little on "enforcement", because rules are important. Call it audits, compliance, metrics, or whatever.

But not more than would be saved without enforcement. Because diminishing returns.

And at some tipping point, ratcheting up cost of compliance backfires, leading to more cheating.

So strive for some happy equilibrium. So that the general population (taxpayers) feel the system is reasonable, if not exactly fair, and overall friction is minimized.

Before it was stripped from the ACA, the price for not having insurance scaled with income. At the lowest end it was irrelevant because of Medicaid eligibility; above that it gradually increased from below-healthcare-price to above. So some people could still save money by opting out, but it pushed them towards the market by making the effective cost of insurance smaller.

(Technically speaking, it was a tax rather than a fine. That mostly mattered for legal reasons, but it did also work that way in practice. It applied to everyone, so insured people had the obligation waived, but the people paying it weren't in violation of any law or regulation.)