When the Walther PPS first came out, it answered several of the requests people had for a single stack carry pistol. As avid shooters and people who want to carry a single stack with good features rivalling that of the Glock platform, the Walther PPS offered very favorable and familiar features that made it a natural pick for those favoring striker fired pistols. Having a single stack, concealable pistol in a market that mainly consisted of DAO firearms was a sure way to get more sales than their competitors due to the rise of people leaning more towards favoring Glock style trigger systems in general. The PPS also brought great durability and reliability that people could count on to help them feel less guilty for using their carry gun as a range toy as well. This specific characteristic was definitely a good selling point for people when the standard firearm was not intended or designed to be used and abused beyond the normal spectrum of shooting it for break in and to ensure general functional acceptability when carrying.
The features of the PPS that made it so appealing was the fact that it offered a platform that was compact, with a trigger that closely resembled what they had come to know on the Glock platform. Also the takedown procedure is very similar. The controls were low profile and yet easy to get to while the competition had big slide stops and safeties that frankly turned off alot of people. But the one thing about the pistol was that it has a paddle release which, in my opinion, offers faster reloads and the ability to actuate it without moving the hand. But with the recent relaease of the PPS M2, the pistol answers the request of the general american consumer to switch the paddle release out for a button release.
The grip of the firearm did what alot of manufacturers still struggle to do. It had a nice and semi aggressive set of serrations that ensured a solid grip without being so aggressive that the grip becomes uncomfortable. The recent PPS M2 grip follows the PPQ grip design in having a very gentle yet secure texturing pattern that covers the grip, as well as an adjusted design f contouring and overall grip shape to fit the hand better.
The sights on the pistol, not only being adjustable, but also designed to give you quick acquisition of your sight picture was a good addition that seperated it greatly from the competition. Many these days say that they do not like the fact that the sights have alot of room on both sides of the front sight in the sight picture, but they seem to think that this doesn't inhibit their ability to make quick and accurate hits on target.
The biggest thing that people found when the PPS came on the market was the fact that this pistol shoots like a full sized pistol. The recoil in both felt recoil and muzzle flip was comparable, and somewhat exceded the soft recoil of full sized pistols. This is a feature that people all over the shooting community were asking for. Even though the overall dimensions and weight of the pistol does not end up beating other pistols on the market, the PPS offered the one thing that was valued most-shootability.
For the many reasons that I listed above, the PPS still conquers the market and sets a standard for how people want their single stack firearms to be designed. Aside from designing a model with full ambidextrous controls, the PPS answers more of the requests for people who enjoy shooting and carry a firearm daily than most other firearms on the market.