Logical for your needs, perhaps. Logical for my needs, perhaps. Logical for the person who has several thousand novels and is willing to wait a few days for the database to be updated ... er, maybe that isn't the best argument. But it may be logical for the person who has a few hundred large books, may it be due to illustrations in children's books or photos in non-fiction books, comics/graphic novels, or PDFs. The Glo HD may have upgradable non-volatile memory, but it is a non-trivial process that is inaccessible to most people.

It is also worth noting that the Glo HD is only the latest model, so it does not indicate a trend. Indeed, the recently introduced H2O does have an external uSD slot. The Glo HD is by no means the only Kobo without an external uSD slot, the older Mini is an example. Given Kobo's tendency to introduce a range of well differentiated devices, I suspect that they will continue to produce and develop models with and without the slot. Then again, it may prove to be an anomaly, like the capacitive touchscreen on the Aura.