The Data Only plans' pricing needs updating. They are supposed to be 'just great value data' and be cheaper than Voice plans because they don't include calls and texts, but that is not the case. At the current pricing, it is better to get Voice plans even if you only want data, as you get more data for the same price, and you also get free calls and texts as a bonus even if you don't use them.
It's not like there are advantages to paying the extra money, like getting a public IP address instead of being put on CGNAT, being able to use a MiFi which we can already do with a Voice plan, higher priority than Voice plans, or removing fair use policies in the unlimited data plan which the Voice plans don't even have (there are people reportedly using 1.5TB of data with SMARTY, highest I've seen being 2.3TB).
It's even worse when you account for those deals you find on sites like Uswitch, and the Data plans are just not worth it at all. Looking at this article covering Data SIM's introduction, it seems even back then its value wasn't as good as Voice plans, so what even is their purpose? There's only this thread trying to theorise why the Data plans are like this.
I think the plans should be changed to be priced lower than the Voice plans, do the occasional promotions with these plans as you do with Voice plans, and add benefits that are clearly communicated such as replacing CGNAT with a public IP address.
(and please don't deprioritise, add FUP or block MiFi devices with Voice plans to make Data Only plans better)