Exactly my findings with my scrap grade DIY oiler. It oils the chain and washes the dirt away. I assume that doing that improves (extends) the life of the chain but I've no way of knowing. If the interior of the chain has built in lube and that's where the majority of wear occurs then oiling the exterior might be mostly a pointless exercise.

Yes, chains have improved since the '30's but it's just as well really as they're still hanging out there in the elements. They had exposed primary chains and valve gear back then as well but they didn't last long (in both senses). What we've got now is the equivalent of saying we won't put a cover over your valves, we'll make them out of tougher steel so you can still see them flapping up and down but the service interval will be increased.

I've heard many times over many decades that the reason most bikes still have exposed chains is because the racing fraternity have them (for understandable practical reasons), so for marketing purposes sports road bikes had to have them (if it's good enough for Hailwood / Sheene / Doohan / Rossi et al). Now that sports road bike sales have all but collapsed the link isn't as strong but we're stuck with them as we're 'programmed' to think of exposed rear chains as normal. The manufacturers are happy to let that continue as chains are cheap. Its always amused me when stuff like last year's 'diamond coated' (or whatever the 'advance' was) chains are announced as it's no better than polishing a t*rd.

Considering that just about every other source of environmental 'pollution' from motor vehicles has been subject to legislative scrutiny over the decades - not only exhaust emissions but things like petrol vapour and tyre particulates for example, I'm amazed that something as obviously hazardous as an exposed moving chain that drips and sprays oil onto the road is still allowed. It can only be because bikes have somehow slipped under the environmentalist's radar (or, I guess money has changed hands. We're too close to the end of fuel powered bike production for anything to change now but I'd be amazed if electric bikes are allowed to get away with it for long.