The truth is that many foreigners are getting their PR application for Singapore, but far fewer are going further than that. Why is that the case? Here are some of the main reasons why.
You can get virtually all of the benefits for locals even without being one. For instance, the only main thing you will not be able to receive is buying a HDB flat at the discounted price and need to get it at the open market rate. But if you are reading this post, you probably have zero desire to live in a HDB, and are probably already considering a condo or a landed property. You need to jump through more hoops and hassles with no additional incentive for you.
Some people say it is a privilege to serve NS, not me. Why not give that choice to your male children instead? Maybe they would love it, and they can still serve it in future. But give that freedom of choice for your child, by just maintaining a residency instead first. In case your child wishes to travel to another part of the world in future, he can still do so without incurring any penalties if he just gives up that up. However, if your child is a local, he will never be able to enter the country without being thrown into jail if he decides to avoid NS. So why drag yourself (if you are a guy) and/or your male kids into this liability by changing your entire status and losing the flexibility?
One of the strongest reasons that many foreigners do a PR application is they wish to leverage the overall stability of our city for both their living as well as their finances as SG is a global financial hub. You can get both of that without being a full Singaporean, so why go through more hassles which is much harder to reverse in the event you or your family members change your mind?
Additionally, we are one of those countries where you are not allowed to hold dual or multiple citizenship. However, your current country probably allows it. So, foreigners realize the great advantage of just having a PR here.
In summary, by being a permanent resident but not a Singaporean, you still get 99% of the full advantages with 0 of the downsides. How amazing is that? Now, before you get too excited or any of the process, make sure that you are eligible first.