sometimes easy isnt the right way changing oil imho is one of the most gratifying/easy/preventive thing u could do stick with stock u gotta think they thought of this in 66 an said ehhh bad idea
Not necessarily. If they thought of it in '66, they probably thought "ehhh, it will cost an extra $ per car." Or, "how many morons will leave it open and blame the failed engine on us".
The biggest motivator for factory production is cost. Why do you think the drain plug on auto transmissions went away? It wasn't because you don't need to change the transmission fluid. Just because the factory didn't do it, doesn't mean it shouldn't be done, or that it won't be better the other way.
I've seen the Fumoto valves before, looks like a neat idea. For me, I've just never thought the convenience is worth the cost, the normal drain plug isn't that inconvenient to me. But if it keeps you from jacking up a lowered car all the time, it might be worth it to you.
As far as the tab getting caught on something, I don't think it'd be all that likely. How often to you hit things in the road with your oil pan?