I just asked Mr. Google why the gas can design changed.
"The whole trend began in (wait for it) California. Regulations began in 2000, with the idea of preventing spillage. The notion spread and was picked up by the EPA, which is always looking for new and innovative ways to spread as much human misery as possible.
"An ominous regulatory announcement from the EPA came in 2007: “Starting with containers manufactured in 2009… it is expected that the new cans will be built with a simple and inexpensive permeation barrier and new spouts that close automatically.”
"The government never said 'no vents'.” It abolished them de facto with new standards that every state had to adopt by 2009. So for the last three years, you have not been able to buy gas cans that work properly. They are not permitted to have a separate vent. The top has to close automatically. There are other silly things now, too, but the biggest problem is that they do not do well what cans are supposed to do.
"And don’t tell me about spillage. It is far more likely to spill when the gas is gurgling out in various uneven ways, when one spout has to both pour and suck in air. That’s when the lawn mower tank becomes suddenly full without warning, when you are shifting the can this way and that just to get the stuff out.
"There’s also the problem of the exploding can. On hot days, the plastic models to which this regulation applies can blow up like balloons. When you release the top, gas flies everywhere, including possibly on a hot engine. Then the trouble really begins.
"Yet let enough time go by. A whole generation will come to expect these things to work badly. Then some wise young entrepreneur will have the bright idea, “Hey, let’s put a hole on the other side so this can work properly.” But he will never be able to bring it into production. The government won’t allow it because it is protecting us!"
https://lfb.org/how-government-wrecked-the-gas-can/
I've seen a lot of gas cans left by the side of the road. Maybe I should stop and check them out, on the chance that someone just didn't want the gas smell in their car, and tossed an old-style one. And yard sales.