The natural way of listing verbs in dictionaries is by infinitive, but this is not the case in many Latin dictionaries. Why? Were there some of the first Latin dictionaries using first person singular as the verb's base form?
First, not all dictionaries follow that convention.
Importantly, though, the infinitive cannot distinguish between 3rd and 3rd-IO verbs, which of the four principle parts, is only distinguishable in the first person present (cf. ago, agere, egi, actus v. facio, facere, feci, factus). Not having that there would lead students to miss that crucial information.