There are several reasons that a Folding bike makes the best town bike for many people.
As fast as most full sized city bikes
You can take inside at work
They will fit in most car trunks, no car rack needed
They adjust to fit small people or large people
They can fit in most closets
If you get caught in a rain storm you can fit most folding bikes in the trunk or back seat of almost any car, taxi or uber. Most bikes fold up in less than 30 seconds.