It’s a question that comes up regularly for this airspace .... notwithstanding the safety arguments for, and against, this approach as these can be assessed .... a key factor is often quoted as being the airborne database size necessary to hold all waypoints versus the fleet capabilities at any one time as there’s quite a lot of metal around that measures memory capacity in kb and mb, and not gb. There’s also logistical issues with separating the 5LNC points given the variety of city pairs here too and proximity of similarly spelled and sounding points at other ends of the NAT.
Also, bear in mind that this airspace is managed by the ICAO NAT Systems Planning Group .... they know very well how often a wrong coordinate is flown etc.
Finally, automatic systems are implemented that check your route using the confirm assigned route message, and a great deal of this airspace is surveilled using space based ADS-B with very frequent updates and route adherence checking (so ATC know before you enter the airspace that your route matches what they’re holding, and if you change route, track or level, they get an alert within seconds of it being input into the MCP - depending on ADS-B equipage - so that they can intervene).