Ya, if you were for instance say, working out in the hot sun all day, and only drinking RO/DI water, the sweat would remove necessary minerals and trace elements from our body, and the RO/DI water would not be replenishing them. I doubt you'd die from it but it may not be the best thing to do.
For sure these RO filter systems were used A LOT for household use.
BUT... I don't think I've seen many household water filters with a nuclear DI stage. I'd think the DI phase is used for specific and necessary purposes only I.E. reef keeping, industrial processes, etc. Did I mention reef keeping?
