I think the majority of it is down to the pre-SaaS customers of the product. 1Password used to have a life time license and would work without any need for 1Password servers. You could backup your vaults anyway you wanted and the various clients would work with a variety of methods for syncing etc.
A lot of long term 1Password users bought this and still use it, but the company no longer really do much to support it having pivoted to completely focus on their subscription offering. Many of their long time customers, many of which are HN users, feel they're getting shafted by the lack of updates etc to those older offerings. From what I understand a lot of the older clients and plugins that worked with the local versions don't get updated anymore. However, I'm only a customer of their subscription offering so someone else might be able to elaborate more.