The bodhisattva vow came from the Shakyamuni Buddha, he made the vow to become a Buddha under the Buddha Kassapa. therefore no school of Buddhism should decline a student just because he/she wants to make such vow, the point with Mahayana is that the main goal in that school is to attain Buddhahood, therefore the vow is very important.

For Theravadins the main goal is to become an Arahant, therefore the vow is not crucial. Don't forget that the next Buddha to teach the Dhamma (Maytrea) will only come in circa 2.500 years, so we are talking about a Paccekabuddha (Private Buddha), a lone Buddha that does not teach the Dhamma.

The bodhisattva vow came from the Shakyamuni Buddha, he made the vow to become a Buddha under the Buddha Kassapa. therefore no school of Buddhism should decline a student just because he/she wants to make such vow, the point with Mahayana is that the main goal in that school is to attain Buddhahood, therefore the vow is very important.

For Theravadins the main goal is to become an Arahant, therefore the vow is not crucial. Don't forget that the next Buddha to teach the Dhamma (Maytrea) will only come after 2.500 years once the current Sasana ends, so we are talking about a Paccekabuddha (Private Buddha), a lone Buddha that does not teach the Dhamma.