The ability to create a deal when a form is submitted requires the deal properties have a counter contact property. For example, if we have a deal property called Property Location, there needs to be a contact property called Property Location that can be used in the form and can be mapped to the deal with a workflow.
We have about 100 deal properties that we would like to be submitted on a form. This has required that we also create 100 contact properties and use this workflow to map them. The ability for forms to directly populate Deal Properties would be a better route with less room for error.
If you would also find Deal Forms helpful please upvote this idea here. https://community.hubspot.com/t5/HubSpot-Ideas/Use-Deal-Properties-in-Forms/idi-p/208361