this is not just Mexico, it’s true in much of Latin America. I haven’t looked at the specifics in a while because it’s a difficult question to ask (“can you buy X drug in Y country *without* a prescription”), but I’ve talked to trans people in Argentina and I think Colombia who do the same, and I occasionally order my hrt through Ifood in Brazil, which is functionally equivalent to Uber Eats.

pharmacies just don’t enforce prescriptions consistently in much of the world. there may be laws stipulating that they do, but where there’s no mechanism of enforcement, or enforcing it comes into conflict with the widespread practice of self-medication, pharmacists do not necessarily check if you have one when asking for a medication by name.

functionally this means many things that technically require a prescription are effectively over the counter, with the frequent exception being psychiatric meds and opioids, which tend to be more tightly controlled.

it’s not in the interest of the pharmacists’ employer to limit sales where most people don’t have consistent access to a physician, and implementing more draconian penalties to deal with infractions isn’t very politically practicable since it doesn’t address the lack of coverage. the US does this, but you can still buy prescription drugs online, which is what this is, just on a more immediate scale.

so being able to get E delivered without a prescription is not necessarily ‘more’ legal in Mexico or Brazil than it is the US or Canada, it’s just an overt manifestation of a mainstream practice of non-enforcement, which is less visible in the US and other wealthy countries because strictly adhering to a model where you need a prescription for anything more than ibuprofen is much more economically practicable in these regions (the costs associated with this model are also subsidized by the profits from private healthcare interests being concentrated in these regions)