Lots of property field types really should have the ability to set default values (e.g. checkbox, dropdown, radio, number).
If we create a property such as "Has Trial Account" on a deal, the ability to default it to no/false would be incredibly helpful and would reduce our number of workflow steps by about 50%.
The lack of this ability means that we have all sorts of stupid branches in workflows that have to test whether a property is "unknown" or "empty" and it has been a constant source of frustration when new people join the company who are not familiar with hubspot. They always say "no way, really" when we explain that to determine if a field is yes/true in a report they actually have to look for "unknown, empty, and no" which in many places in HubSpot is not possible. For example, contact lists, I can't do or conditions which means that I can not reliably filter on a field.