The advances in Medical technology for certain diagnostics has changed particularly with respect to thermometers and taking temperatures.
What is currently available can range from Quick read to non invasive such as scans.
That has to do do with what is available for that purpose…
…how a temperature is measured via the route may still well be the rectal route/ method, albeit not with mercury thermometers which were gone after years ago for the “ mercury hazard” NOTE: They are still out there ( auction sites)
But it is still likely that in medical venues, for policy reasons or patient situations, rectal temperatures are and may as required , be taken.
In a domestic setting, rectal temperatures may be the preferred method for adults
In a primary care physician’s practice, there probably are those care providers who prefer to still take their adult patient’s temperatures rectally; though it may well be a nurse, or other medical assistant actually performing the procedure.
So, in today’s world of temperature taking, technology has impacted to some degree that protocol.
But I think for the most part the taking of a rectal temperature on an adult , though at times, necessary, is not common.
Key point: As I said there MAY be times/ reasons for a rectal temperature taking.
My last comment: Recently when hit by a UTI I ran a 104F temperature. I got a nurse on a hotline who when I told her my temperature and that it was a rectal measurement, she commented that was the most accurate. It was not the first time I heard medical personnel say that.
On her advice and urging I got to an ER got diagnosed , treated with antibiotics, and recovered. All temps in the ER were by ear.