It's not about how you feel paying your gran; it's about how she feels being paid by you.
The key factor is that people who have a sense of belonging or ownership will donate their time and expertise. People on /r/AskHistorians go to extreme lengths to provide ultra-high-quality answers for free because that's what it takes to be part of that community. The one time I felt like I actually had something to contribute I started my comment (a reply to another comment, there's zero chance I'll ever be qualified to provide a top-level response) with "It's an amazing day, I actually have something to contribute here!" And many people start their comments that way.
A paid environment -- especially one where the compensation is likely to be trivially small -- is far less likely to engender that sort of participation and support.
The key factor is that people who have a sense of belonging or ownership will donate their time and expertise. People on /r/AskHistorians go to extreme lengths to provide ultra-high-quality answers for free because that's what it takes to be part of that community. The one time I felt like I actually had something to contribute I started my comment (a reply to another comment, there's zero chance I'll ever be qualified to provide a top-level response) with "It's an amazing day, I actually have something to contribute here!" And many people start their comments that way.
A paid environment -- especially one where the compensation is likely to be trivially small -- is far less likely to engender that sort of participation and support.