Exactly. A technology for new projects should be selected based on what best meets the requirements, not on what is currently in vogue. PI Web API is a good choice for software that will run on non-Windows platforms, or where it is not possible to have a locally installed AF client package (like some web servers). For Windows based software, my first choice is always native AFSDK, as it is both performant and is fully supported on modern versions of the platform. We have written an application that requires cross-platform support, so it was developed in Java and uses PI Web API for data access to PI. Right technology for the requirements.
Whilst I am still delving into the PI Web API, my first impression when it came out a couple of years ago was that it was good for 'lite' access to PI data. The functionality has improved the past few releases, but it still isn't as full-featured as the AFSDK (nor should it be). Again, depending on application requirements, choose the technology that best meets those needs.