I believe that is just to increase participation for Nationals because the weights used for LW Open classes are not always appropriate for 175 lbs competitors.
When I won 200 lbs Nationals in 2007 (largest nationals to date) we had over 20 competitors in the 200 lbs class and more than 80 overall LW's. Even though I won the 200's my overall placing was maybe top 15. The 175 lbs Champion placed lower in the overall. In 2008 the 200 lbs Champion was top 5 after day one but fell a few placing on day two, the 175 lbs champion was never in the top 10 overall out of 48 competitors.
With this in mind I do not think that it would ever make sense to award an ASC Pro Card to a 175 lbs or even a 200 lbs competitor. Even the top guys in those divisions would have trouble hanging with mediocre 105 Kg competitors, so giving them a Pro Card would just set them up for failure at the next level - and just about every Pro contest would have weights that would not be reasonable for a 175 or 200 lbs competitor.
It would be great if there were a 200 lbs pro class but the participating in that class has fallen over the past couple of years and those individuals would not be able to compete in the ASC 105 Kg group so it would require a lot of work and it would be tough to draw fans since the average HW would be much stronger than a 200 lbs Pro. One of the things about the 105 Kg that draws attention is that there are a lot of great athletes who in many cases can place top 3 in NAS HW contests - while giving up 50 or more pounds to the other competitors.
That is just my opinion but I have been in the lighter classes and worked my way up, it was not easy but if you want to compete in the ASC the opportunity is there for you - just need to work hard and pack on size/strength. Otherwise a National Championship is still an outstanding achievement and there are very few people who have won more than one (Tom Kaufman was 200 lbs Champ in 2005 and 231 lbs Champ in 2008).