Normal people have to read a booklet, memorize basic things, take a written test, take an eye test, and drive around the block. All can be done in the span of a day. License acquired, go drive whatever 9,000lb vehicle you want in the way you see fit.

Commercial vehicles require a commercial license to operate, which requires training and one at-fault accident may revoke their commercial license. Plus depending on the loads they carry they can be worth millions of tens of millions. That's why you don't typically see 53' flatbeds going 20 over the limit and weaving in and out of traffic. Sometimes it can get sketchy if they're close to their destination and it's a rush against their (electronically) mandated off-time, but also one speeding ticket can put their license at risk.