I know you said you're still on 1.5, but if you ever decide to make the plunge to XF2, there's always these solutions:no hash-tagging, no ecommerce solution
[DBTech] DragonByte User Tagging
[DBTech] DragonByte eCommerce
If I was to hazard a guess - bearing in mind I do not work for XenForo so I have no way to know how they decide which 1st party add-ons to produce - the reason why they haven't created a 1st party eCommerce tool is that it has limited use. I would wager that the percentage of forums that have no use for an eCommerce tool is vastly larger than the percentage of forums that do have a use for an eCommerce tool.
On the flip-side, the percentage of forums that would have some use for a Media Gallery and/or Resource Manager / download repository (without payment) is probably larger than the percentage of forums that have no use for such tools.
Every forum could probably benefit from having a gallery (gaming forums: game screenshots. car forum: ...well, cars. etc).
I totally understand how frustrating it can be to have to go to 500 different sites to buy 500 different products rather than just being able to have everything you need as a 1st party solution, but I think it's important to look at a potential lack of ROI as part of a reason why they might not have created such a 1st party tool yet.
I think this could be an interesting discussion, so if it's something you want to discuss further we should probably take it to another subforum so as to not derail this thread too much