It would be a little awkward to decide what "time" to start the day though, but it's not like midnight is the greatest time to start a day either.
I don't think there's particularly any advantage either way, but everyone would have to re-learn their tricks for dealing with timezones and instead learn tricks for dealing with the lack of them.
The more globalized your daily affairs are and the more "scientifically" you think, the more you will be drawn to a unix-time style of thinking. "Humanistic" times are designed to unify everyone around particular rhythms that have the same "names" for when work starts (9), when work ends (5), the middle of the day (12/noon), etc, regardless of where they live (and at the cost of actually meaning the same time wherever you live).
Those are even less meaningful if your schedule is based in weeks and months rather than days, though.
The humanistic factor of time zones is most useful for in-person, social stuff. In every other case I would prefer to tell someone what GMT time I wanted to get on the phone with them.
The resistance is cultural, not because people can't deal.
I'd love to be able to say we could schedule a call next Tuesday at 1900 and everyone knows exactly what that means without having to consult a look-up table.
Imagine coordinating between teams spread across Arizona, which doesn't do DST, New York, which does, Brazil, which does but for the southern hemisphere, and Europe, which has its own thing going on. Getting people on the same page is not trivial, each week can be a whole different set of time-zone offsets.
It'd be like switching from °F to °C which, once done, is not a problem, except of course if you have a stubbornly regressive administration like the US did in the 1980s.
Very few people are that isolated, and those that are probably don't care what time it is.
The resistance is cultural, and, let's just say people have strong opinions about these sorts of things. The fight against Celsius would be similarly difficult.
Good luck with that.
Honestly, it only takes one generation, they'll deal with the change and then the rest is history. of those ~300 million people, 20% are old and will never change, they'll always use legacy time, and 40% are young enough it's no big deal. The remainder will be inconvenienced, but will get by.
Besides, it'll give people something to complain about.
One of Obama's biggest missed opportunities was day 1 declaring the US was metricizing. This would've given conservatives something other than tan suits and mustard to rage against for the subsequent four years.
Moving to metric units would still result in the same fight, even if there is a greater possibility you could actually win.