I suspect there is a balance between too many miles / points on the books and maximising cash revenue (to the detriment of award redemptions.) Also, demand for travel has been high so airlines have had little motivation to open up award space.
One solution that is now ubiquitous is the ability to use the miles/points to pay for part of a revenue ticket, which is in a sense selling those points/miles back to the customer for a higher price. If you sell the 100 points to a credit card company for $1 and then they are redeemed at a value of $0.50 off a revenue ticket - that's a significant margin. (I've made up those numbers, of course - but you get the point.) There are other examples too, like redeeming points for duty free purchases.
The point being that making award redemptions easier for pax is likely very low in the priority list. They may not be actively discouraging that (or are they?) but when it comes to investing money in producing better tools, I suspect the business case to be pretty unattractive.