With most other things, you know what you are getting. With software, you are not sure.
For this one, specifically, I'm not sure if I want my wallpapers to change all the time. Maybe it would have network issues. Maybe it would show ads. Maybe it has something malicious in the code. Or maybe changing wallpapers would sometimes make it hard for you to see the icons on your desktop.
Do you really want to pay for something with all of these uncertainties? Besides, writing a python script that would do the same might take half an hour, but it would be fun and you would know exactly what it's doing. This is in contrast to making coffee, which - at least for me - is anything but.
For this one, specifically, I'm not sure if I want my wallpapers to change all the time. Maybe it would have network issues. Maybe it would show ads. Maybe it has something malicious in the code. Or maybe changing wallpapers would sometimes make it hard for you to see the icons on your desktop.
Do you really want to pay for something with all of these uncertainties? Besides, writing a python script that would do the same might take half an hour, but it would be fun and you would know exactly what it's doing. This is in contrast to making coffee, which - at least for me - is anything but.