Do you in Microsoft consider the possibility to add Power Pivot to all versions of Excel? Taking into account
- you in any case has the engine inside the Excel;
- user interface to work with it is free for Power BI Desktop;
- in Excel without Power Pivot you may load data into data model (G&T or PivotTable); create relationships from UI; add measures using DAX (PivotTable); make more complex DAX calculations through Table->Edit DAX
All above is workaround and don't give full Power Pivot functionality, but workable. Of course, if you have statistics what quite a lot of people shifted from version like Home on Pro only due to have Power Pivot such separation could make sense. I'm not sure in that, but who knows. Only Microsoft.