Why aren’t Magento sale grids using Mview (and indexer)?

By default Magento implement Mview/indexer for some grids for example customer grid.

But for sale grids (sale, invoice, credit memo, shipment) Magento use a cron job to insert/update new data (if async grid were enabled).

So why is there such difference? Magento decides the solution based on which conditions?

Thanks in advanced.