Inline styles is the best way to style your components, the people just gets obsessed with that because seems weird but it's just that, see below:

1 - You don't need to worry about your styles don't being applied or overwritten by some theme from some UI lib.

2 - If you want to rewrite a style for a component is just to find that component and change its html, on non inline styles you need to find all css files affecting that component and if you did you're not sure if it bugged others components using the same classe you've change, have you ever seen a css with 500 rows of code?

3 - On non inline styles you have to ensure class or id you're creating doesn't exists in your project if you wanna make something new, it's a hell, and you still got to have criativity to name it classes.

4 - Last problem would lead you to use css libs, it adds extra dependencies to your project, using inline styles you don't need about learning sass etc.