Not everyone wants to be married or even in a relationship.
Solo persons are often alone by choice. Others may just not have found the right person.
There are couples who don't want children, or can't have them, and some who don't want to be around children.
Solos and couples are badly served in terms of habitat even though their discretionary income is important to the local economy. In the most recent census, one quarter of all households are solo, in contrast to 5% in the 1920's.
In the MarketTown, it is expected that some villages will come together that are about the solo and couple life, rather than families.
Some of this is a design question. One attractive model is borrowed from the older Oxford & Cambridge Universities residence model. Individuals own a small, comfortable apartment, but most of their meals are taken in a dining hall - not a restaurant or a co-housing design, but the classic, elegant high ceilinged room with long tables where food is prepared and served. In addition, these facilities may have large commons rooms and club rooms, with comfortable spaces that include areas where one may signal privacy wanted... sitting in public, but reading a book, and other places where conversation would be welcome.
Other forms of solo housing are more transient... the breakup of a relationship often results in solo persons, but once they recover, they are looking for a partner. These accommodations may involve rental units rather than owned.
The youth zone is a special form of solo housing. Intended to enable young people to afford to buy a home once out of school, youth housing is very small, easy to maintain and specifically designed for a solo person. In the original concept, it was expected that youth housing would be mixed in with the general housing in a village, but when asked, the youth said they would prefer their own area - the youth zone. They wanted to be able to dance in the streets and not bother anyone - to have a climbing wall and other sporting activities, and to be concentrated so that it would be easier to meet other people their own age.