Working as a mobile developer, I created multiple apps during last couple years for companies I worked for, and eventually for personal projects. It sounds logic to me to mix development and a bit of marketing as I was always interested about how to get more traction, how I could improve acquisition, or if the app had a great retention rate, etc. Once, someone answered me “Probably best is to do what you are best at” but I guess without trying you can’t be better at it.