There is a big difference between "often not practiced" and "not really practiced [ever]". The former is true, the latter is not.
This is not true in my experience (I have designed and run pharmaceutical clinical trials in humans). Can you give some examples?
Some treatment trials do compare the existing standard of care vs the new one rather than placebo against proposed treatment, but those are certainly controlled studies too.
I do know of cases where a control is impossible, such as some surgical procedures, though even then sometimes sham surgery is performed (this is controversial). Those are singly-blinded controls as the surgeon knows.
For example, Newton laid out classical mechanics. Which very adequately modeled most things moving around in scales we could observe. Except Mercury's orbit was a little fucky. Now, one new model could be that "Classical mechanics works everywhere but on Mercury, where they have different physics", but eventually relativity was postulated, and calculated to predict Mercury's orbit to within our ability to observe it. Rinse, repeat, for things like QM, orbital mechanics, etc, etc.
Heck, there's a pile of inconsistencies in our current models. Neutrinos have mass, the universe's expansion is accelerating, and where's all the antimatter?
- Cherry-picking of data.
- Flawed or missing controls.
- Lack of replication, and in the few cases where it's attempted, failure to replicate.
- Non-publication of failures.
- Publish-or-perish providing huge incentives to publish junk.
- Peer review being an old boys club that enforces the party line.
- All funding coming from few sources that tacitly use their funding power to fund only those that toe the party line.
- So much basic science having been done by now that the remaining science to do is generally expensive to do, thus inviting the above funding / control problem.
- Dogmatism.
- Media attention.
These are the problems that plague science today. Some of these have been there for a long time, like dogmatism. There are people alive today who were taught that the continents don't move, and that noticing that South America and Africa fit together and concluding that they must have moved is nonsense of the highest order. There are people alive today whose treatment for Polio was not physical therapy but immobilization. The list of dogma, old and new, is long. The malign ways in which some lords of science fiefdoms defend their dogmas have not gone away in spite of Popper's method.
In junior high school I remember getting taught about the scientific method, particularly the use of controls. I wrote 5 papers and didn’t use a control in any of them (it wouldn’t have been appropriate.).
Even in cases where people obviously should use controls, such as clinical trials, they frequently don’t. There was that paper where the measured vitamin C levels of COVID-19 patients but didn’t compare it to a baseline of people who were not sick, which is problematic in many ways.
When they do meta-analysis by the Cochrane methodology they usually throw out at least half of the studies at the beginning because of glaring methodological flaws. Practically it is not much better than anarchy in terms of what gets funded and published.