There are many ways to regulate too. SSRIs are not OTC for the same reason.
There are many drugs a GP can prescribe that are just as dangerous or more so.
There is a reason SSRI are schedule 4 and not schedule 2 . They cannot kill you the same way [1]
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[1] While there is a lot of politics in the classification and putting weed or LSD in schedule 1 is very questionable the list is generally medically accurate.