The Reason Why Are Trucks Getting Bigger

I always thought it was a combination of masculine insecurities and one upping your neighbors.

Edit: lifted trucks, after market front bars, louder exhaust with larger exhaust tips, truck nuts, American flags or thin blue line flags covering the rear window.. None of these are from government regulations

Then why don’t people buy class 8 semi trucks?

Nothing in the parent's hypothesis implies that the normal mitigating factors like cost/practicality don't apply.

Also, size is only one prominent factor in masculinity. E.g. a pickup truck is frequently seen as more masculine than an RV.