That's not true generally.
Perhaps because of this misconception we are missing out on a paradigm shift, testing technology needs more money but first get comfortable with anyone using the test and making mistakes, which includes the real poor, including illiterate people.
Because medical has been locked up for so long, researchers and governments aren't looking at people looking after themselves.
The pandemic planning stuff I've read from before this year seems to suffer from a number of assumptions that were violated by covid, from asymptomatic transmission to the long lead time. E.g in MERS or Ebola or even flu, the infectious but asymptomatic period is more like Contagion. You don't have to worry about infected people wandering around town for a week or two.
Most planning mentions the need for having tests, and quickly gathering materials etc, and then moves on to tactics for containment and vaccine development. Where testing is focused on, it's as a way to differentiate between people who have symptoms but are actually infected with a non-panfemic disease, so that resources aren't wasted quarantining them. I haven't yet found a scenario studied with a long lead time and possible low level or asymptomatic presentation as standard.
It is possible.
Listen to episode 640 of This Week in Virology[1] for details.
[1] - Starting at about 6'20" - https://www.microbe.tv/twiv/twiv-640/
http://traffic.libsyn.com/twiv/TWiV640.mp3
It should play in any media player.
Bloomberg: You seem optimistic researchers will succeed in coming up with vaccines. How do you assess the prospects and potential risks?
Stohr: The coronavirus is not a particularly difficult virus to handle. Even the conventional vaccines could make a difference, and we have different approaches, vector vaccines, mRNA. That is very promising.
https://www.bloomberg.com/news/articles/2020-07-18/covid-mos...
The thing I just can't understand is why they didn't require everyone back then to wear condoms all the time, regardless of whether they were HIV-positive. Those people were so callous in their regard for human safety!
EDIT: Actually not quite. To elaborate a little further - it has become understood that it is just and reasonable for the state to have jurisdiction over interpersonal interactions that involve money (though the converse is not necessarily implied) - this is 'the market'. Thus going to the store operates under a different regime than going to a friend's birthday party in their own home. Your example would equate to the state mandating condom usage with prostitution, assuming that was legal in the first place.
What you get up to at the store can be regulated by the state - what you get up to in the bedroom (without financial exchange) should not - assuming meaningful consent
But to address the absolutism in your question. If everybody in possession of a penis wore a condom at all times (a) they'd get nasty and possibly gangrenous, [so i'll assume you mean "when the penis is deployed in/on/around a second party"] and (b) it would reduce the birth rate by about 90%.
That would be about as likely as everyone wearing a mask at all times.
> The thing I just can't understand is why they didn't require everyone back then to wear condoms all the time
It wasn't mentioned in "Contagion" for instance.
A vaccination or cure was always known as not possible but the media pushed these false hopes.
In part I suspect this is the usual medial malpractice of doctors keeping their profession wealthy and keeping everything they can tied up and regulated.
I'd be interested to look at HIV and testing in the 80/90s to see whether at home tests were stopped by doctors or technology.