This was the whole point of my website back in the day so I feel like I have a good pulse on why they went this route given I read thousands of warnings over the course of those years. A vast majority of severe thunderstorm warnings are of the 58 mph / 1" variety. Similarly, a high percentage of tornado warnings are radar indicated. A lot of those warnings come and go with few reports to verify them. Identifying the more significant threats, in theory, might cause people to take the more sternly worded warnings more seriously. After all, a tornado on the ground is a more certain risk. Furthermore, the more significant warnings are far more often verified with real damages related to them so it is more critical that people take the higher risks more seriously.
My worry is that people won't take the lower level severe warnings and tornado warnings seriously. In Louisiana, that can be particularly dangerous on tornado warnings. Sometimes strong tornadoes can materialize and disappear within a few radar scans. The Bush tornado a few years back (May 2011, an EF3) is a good example. Also, a few years ago we had a 1" warned hail storm pour a small path of more significant hail in the middle of my neighborhood. We had some new roofs come out of it but the area of coverage was maybe 10 homes in a neighborhood with 200 homes.
The criteria for SVR storms are set where they are for a reason. 58 mph will take down trees. 1" hail causes damage. We have to educate the public on that reality.