The U.S. Libertarian Party does a better job of representing libertarian values in general than the two major parties, but the Libertarian Party platform does not encompass all of libertarianism, just like how there are conservatives who disagree with parts of the Republican Party platform and liberals who disagree with parts of the Democratic Party platform.

Since the first-past-the-post voting system used in most U.S. states makes it difficult for third parties to gain traction, most politicians who prioritize winning elections run under one of the two major parties. A libertarian candidate who focuses on reducing taxes is more likely to become elected on the Republican ticket than the Libertarian ticket. A libertarian candidate who prioritizes legalizing marijuana will stand a better chance on the Democratic ticket than the Libertarian ticket. The goal is to push for changes that would advance the libertarian agenda on specific issues while maintaining the status quo party line on other issues, since it is easier to enact targeted changes than to fight on all fronts. Political candidates who choose to be affiliated with the Libertarian Party need to be sufficiently radical to reject the two dominant platforms that are much more likely to win them elections.

Voters know that third parties including the Libertarian Party are disadvantaged in U.S. elections, and in races that Libertarian Party candidates are certain to lose or do not participate in, many libertarian voters select the candidate from one of the two major parties that they believe would do the best job advancing or preserving the parts of the libertarian philosophy that they prioritize. This is the most effective short-term voting strategy when voter prefers one of the major party candidates more than the others. In the long term, libertarians in the U.S. support ranked choice voting and other reforms that would empower third parties like the Libertarian Party. If the Libertarian Party does manage to gain traction, its platform would adapt to become more moderate, mainstream, and pluralistic to accommodate its larger voter base and encompass more of the libertarian philosophy.

There aren't many surveys that focus on libertarians, but this 2014 one from the Pew Research Center shows that self-described libertarians tend to be more diverse and less radical than you perceive them to be:

https://www.pewresearch.org/fact-tank/2014/08/25/in-search-o...