“EARN” or “BUY” a certification?

As a non-native English speaker, I have worked very hard and have studied many papers and book to deserve the PSM/PSD certificate, although I have near 30 years of experience in software development.

There is an easy way for me to attend an expensive course to get another scrum certification even if I just sleep in the corner of class room.

I really wonder why people here having years of projects’/products’ experiences choose a hard way to earn a certification instead of buying a certificate?

Thanks for any input!