What are the benefits of universal adult franchise as compared to selective franchise?

One benefit is that if the whole population can vote, then the whole population will feel included in the country and will want to contribute to it. I

Additionally, if there is a group that is excluded from voting, there might be unrest and conflict because this group could clash with the other groups, demanding these rights.

Finally, the decisions will be more informed and will take into account everyone's opinion, not just selected people's