I guess some companies like to do this. I would say it's more of a company culture. I used to be confused as well: why are they testing me with those basic algorithm/programming questions? I personally guess there could be following possibilities that they asked those questions:
1. From some interviewers' perspective, they may think in this way: you said you have many years working experience and you've done so many projects. There is a low chance that I happen to be very very familiar with your projects. So you can say whatever you want and I might not still be able to get what exactly you did and how well you did it. So I pay more attention to those basic stuff as well. Good understanding of the fundamentals is essential to good work.
2. Some companies pay much attention to find out if a candidate is smart or not. So they think one way to find it out is to ask you those logic/algorithm questions, and see how you think, how you solve it and find your solution. They don't care that much about the work/projects you did, because they usually might not have a criteria of telling how smart you are from your specific work/projects.
I guess as a candidate, we might have to prepare for both the basics stuff and our specific working experience. That's pretty much the reality.