I have extensively used this as a feature and know a few other people who do. Here are some links where people have used the feature.
viewtopic.php?t=11993
viewtopic.php?t=7954
Here is a youtube video that mentions the feature:
https://www.youtube.com/watch?v=0u1aG9bsybI
Some other slicers also support changing the width of the first layer of the raft such as ideamaker (although I do not like the way ideamaker also changes the spacing of the lines).
When searching about this topic I could not find a single post requesting this change so it seems like the simplify 3d team saw this as unintended behavior and changed it without realizing that it is still an insanely useful feature. Perhaps the feature could be added in the "additions" tab as "raft first layer width" if they do not want the first layer width in the layers tab to affect the raft.
This feature is especially beneficial with materials that have high coefficients of thermal expansion (like abs). Being able to adjust the first layer width for rafts really helps with adhesion. With the release of 5.0 there have been some really cool features that I would like to use but I am still stuck on 4.0.1 as the print reliability is still much better for me with thicker first layers on rafts. If this feature was added I would upgrade all of my licenses to V5
