getting my own authority/mc number question

Similar problem I’m an owner operator and wasn’t sure if I should apply for mc number they said I ddnt since I’m just working in one state ... it gets me confused

 

Chrontar, under 10,000lbs needs nothing,even crossing state lines,FMCSA website claims you need $300,000 liability....but there no law to back it up,trust me I looked....your mail man delivers pacakges without dot or mc and your mail comes from all over the country(crossing state lines)...amazon flex is a bunch of cars, trucks, and vans delivering packages in every city for amazon that come from all over the world...under 10,000lbs was put there for a reason, just don't haul hazmat or passengers and your set...oh and you cant get MC numbers without getting DOT number,and you don't need DOT numbers ight