Lowering fevers is not necessary in any way, does not protect, it does not help heal, the best you could say is maybe it makes a baby (and child) a bit more comfortable. But in exchange the illness lasts a little bit longer.
And this is not my personal opinion, this is what the best available studies say: fever reducers have no medical value.
"The most consistently identified serious concern of caregivers and health care providers is that high fevers, if left untreated, are associated with seizures, brain damage, and death. It is argued that by creating undue concern over these presumed risks of fever, for which there is no clearly established relationship,"
https://publications.aap.org/pediatrics/article/127/3/e20103...
Also not sure if you have a kid but I don't think it's a foregone conclusion that making a sick infant comfortable is not worthwhile.
"It should be emphasized that fever is not an illness but is, in fact, a physiologic mechanism that has beneficial effects in fighting infection"
"and limited data have revealed that fever actually helps the body recover more quickly from viral infections, although the fever may result in discomfort in children."
"There is no evidence that children with fever, as opposed to hyperthermia, are at increased risk of adverse outcomes such as brain damage."
> that making a sick infant comfortable is not worthwhile.
Keep in mind in exchange the illness last longer. There are other ways to make a sick infant comfortable. You nurse them, you hold them, a cool cloth on the forehead helps a lot. Some babies like the vibration of a car ride, parents usually know what makes their baby happy - the hard part typically is finding time to focus on doing that. Obviously it's easier if they sleep in their crib (and for some parents that's the best option).
But what you should NOT do is think "My baby is sick I have to give the baby Tylenol!" You don't. (I've even seem parents wake their baby because it was time for the next dose!) A bit to help with comfort? OK. But the main thing is don't think you are treating their illness.
Tylenol is not for treating the illness. Maybe the parents you're referring to don't know what it does. It is meant for decreasing the intensity of the symptoms. One of those symptoms could be a fever and potentially the body aches that come with that. But then you have to define the word "fever".
Giving the baby Tylenol as you're describing is probably not a good idea. Using it as the tool it is meant to be I would say is.