I would not say it is always good to bevel. If someone who is not fairly well skilled in welding bevels a component that is say 10 ga. and will not be able to see the back side of that component to verify that there is no overlap, slag inclusions, etc. has a good chance of making a weld that would be less durable than one that was fillet welded and able to be fully observed and repaired as needed. I have no doubt that you are fully capable of achieving complete joint penetration in a non backed beveled edge, but you're a skilled craftsman. Most people weld on occasion and will probably do best with simpler fit up
. Your assemblies probably do benefit to a degree from bevels.
The majority of welds that are required to be full pen on structures that are governed by D1.1 are required to be non destructively tested even when performed by qualified welders iirc.
That's not to say that there aren't a lot of good welders who are completely capable of doing anything that would ever arise on a project truck, but full pen welds, especially out of position without backing are a bit of a specialized operation. The average amateur who only welds on occasion will have a much better likelihood of achieving what would be considered an acceptable fillet weld than they would of doing the same with a full pen. That's why a person who is qualified for full pen is also qualified for fillet, but not vise versa.
