I intuitively sympathize with the view that if you opt out, you’ve opted out, and have no right to expect anything. I certainly do not. But I would also be grateful if the local school offered such options, not only because we might use them, but because it would mean going beyond what they have to do.
The answer in part would seem to come from a the role sports plays in the particular community, as well as how we generally understand sports in schools.
There are communities and sports (particularly football) where the sports program of the high school is seen as representing the whole community. Everyone goes out to watch the team; everyone cheers, etc. For communities and the select sports they celebrate (basketball would be the other obvious one), then making accommodation for the home schooler might make sense. Home schooled or not, on Friday night there is only one game in town.
In other sports, and in the schools I’m familiar with sports plays a somewhat different role. It functions as a reward for work in the school, no grades no play. The team is a place for development of young men and women in the context of their school. In this sense the sports teams are comparable to other extracurricular activities such as debate.
Along this same line, there is also a community aspect. It’s not just the student athlete that is engaged, it would be the parents. The Boosters group begins long before your son joins the team, starting at the science fairs, the PTA meetings the the little fund raisers you did together back in elementary or middle school. Sports is one more instance of this ongoing life, parents working together to support their children. Speaking as one on the inside of the high school, the homeschool student and parents could be on the outside. Welcome, but on the outside.
So I lean against having the home school student on the team. The team does not belong to the community so much as to the school. And if you are to represent your school, you finally need to be a part of that school. (Interestingly in our neighborhood, the local homeschool association actually provides sports teams, a marching band and debate.)