Because it is forms for singular third person and plural third person, not for singular first person.
Because of the fact that this verbs included in the verbs motion in Russian and it gives a unidirectional meaning.. for example, Куда ты идёшь? Я иду в гостницу.. he is heading towards the hospital.
Куда ты ходишь каждое утро? Я хожу в гостиницу. A repeated action or habit.
Another usage, я иду по городу ( he is walking towards a certain destination or without making sharp direction changed or postpone)
Я хожу по городу ( I am just walking around the city without a spesific direction or destination, even if I have a destination, I am not following a strict path)
The same usage is valid for ехать and ездить. The former takes after the same description as идти and the latter as ходить but only difference is they are being used while on a wehicle.