As noted by others, it is that great.
I'm 100% sure you're overconfident and just made that number up. Based on DHS data, a quarter of non-immigrants coming by plane visit Florida, and two-thirds are visiting one of five states, which are big tourist destinations (NY, FL, CA) or border states (TX, AZ, CA, NY). (One site I found says nearly half of families visiting the US go to a theme park, and most of them to a major one.) Around 20% aren't even visiting for pleasure (business, students, moving to US as temporary residents, etc.). These 80 million per year (pre-covid) also mostly don't count land admissions from Mexico, which were about 350 million per year, many of whom go back and forth for work, nor land admissions from Canada, which are over 10 million per year. And 20 million of the 80 million are from VWP countries, and if you add in Canadians that's a lot of people who can afford a week or two in the US without needing to stay with family or friends. While some of all these groups are visiting family and friends, 70% seems way too high, and I could not find that number anywhere.
This is hilariously wrong. DHS's overstay report says the number of overstays from NIV who entered by sea and air is at most 3.67%. Within that, 0.25% did leave the country within the fiscal year (just late), and another 0.38% adjusted status, brining the total down to 3.04%. (Some may have adjusted fraudulently, but some did not, including some K-1s who hit 90 days and dual-intent. Having at most 0.2% or 0.3% of entries use a NIV to arrive and then fraudulently adjust status is very, very small.) They may not capture all departures too, but even if it's most, that's around 3%. Hardly a majority. And around 20% of total overstays are just from TPS from Venezuela. VWP overstay rate is 1.15%, non-VWP is 7%, student/exchange is 3.5%, and for arrival by air/sea Canada is 0.5% and Mexico is 3.5% (but Canada in Mexico do not give DHS exit data when their citizens drive home, so those numbers are probably lower).
As noted above, it's at most a 0.3% problem. One in 300. Is it worth this system for <0.3%? Most, I bet, think not.
The most pessimistic cost estimates to governments are under $500 per American per year for all people without legal status, about equal to the benefit that international tourism brings to the economy. Take out illegal entries (rather than overstays), that's around $300. The less pessimistic estimates are less than that, and include benefits, like taxes paid; one could also include growing the economy. And since many people in the US without legal status arrived in prior years, the cost of new overstays per year to governments is probably something like $30 per American. If tourism dropped about 5%, this would hurt the US economy as much as the savings created.
These measures are not there now. There were some temporary measures between June (when the border reopened to foreigners on tours) and Oct 2022 (when it reopened generally) due to covid. Right now, as an American citizen, you can buy a ticket to Japan today, arrive tomorrow and pass through immigration at the airport, no visa or registration needed. (You may need a return ticket, but they don't always check.) All you have to do is note your first night's address of stay. Some countries, like China, North Korea and those of the former Soviet Union, for example, require you to bring addresses of where you'll stay each night to get your visa (though you can sometimes change later), and then hotels or friends/family will report you to the local police every night so it's recorded where you are. I doubt that would be popular for many going to the US: the land of freedom making you register with a tour company and report your whereabouts every night.
You're welcome to have strong and passionate opinions on this, but lots of your "facts" supporting your opinions are just made up and not even close to reality. You seem to think overstays are the majority of visits, when it's actually in the low single digits, and that it causes massive financial harm, when it's actually at worst under 1% of government spending, and probably a tenth of that. It's definitely the case that there are issues, and there are ways to adjust the system. But given the scale of the problem compared to the scale of this solution, and how much of an outlier the US would be among developed countries, I think most would rather just keep what we have and work to make smaller changes (like mandatory E-Verify, which would likely severely cut overstays).