One of the reasons this is more common with Dolmar, or any or the second tier brands, is that the typical dealer doesn't move that many saws. Therefore there is no business case to be made for tying up a lot of money in parts that aren't going to sell. A well established Dolmar dealer is more likely to have a decent parts stock that a fairly new guy. And for any brand, a shop with a good pro/serious user business will almost always have a lot of parts. Cause if he doesn't, he's not going to have those customers.
We ran into this problem ourselves when we gave Dolmar a try. We have tons of Husky and Jonny parts, and there is a healthy number of saws out in the field to justify that parts inventory. So, we sell PLENTY of parts. We didn't sell that many Dolmars, and there was no way we could have a comprehensive parts inventory on hand to support them. Need a Husky part? We got it. Needed a Dolmar part, we'd have to order it. Not good for my reputation, and hardly fair to the customer. A customer expects parts support, and doesn't want to hear, "But I only sold a handful of them and that's not enough to stock many parts."