Pointer-based devices have the benefit of being able to use the cursor's hover state to reveal information (for instance, labels on buttons). While this can allow for more minimalist-looking interfaces on desktops, it's a really terrible anti-pattern referred to as mystery meat navigation when on mobiles. When you hover over a button, you're not committing to clicking it. However, because mobile devices lack a hover state, users must necessarily commit to a user interaction to understand what a button even does. Particularly, given how slow the mobile reading experience can be, users tend to be a lot more cautious before committing to any action that might cause the page to reload.

The solution is simple--unless using incredibly clear iconography, label your buttons on mobiles.