I've talked about this situation with the sensei and he doesn't want to interfere with pairing up. I'm too shy to confront other students and tell them what I think.
The dojocho sets the tone that creates the culture of a dojo. In many dojo, the dojocho explicitly asks or directs more advanced students to team with newer students and this fosters an atmosphere in which people rise together.
"Not interfering" with pairing up means he sets no expectation. To me this is akin to having no expectation there will be etiquette expectations, hygiene expectations, other behavior expectations...it is a lack of leadership.
Hopefully there is at least one class a week where more advanced students can practice without beginners, so the overall practice in that class is at a higher level?