They're slower if you spend cpu-intensive time in the interpreter. If you're calling wrappers for C functions then there's little difference. For example, sending SPI or I2C data are effectively identical. Same too if you want to render a QR code using a C library for example [1].

So if you ever find that you need more performance you can drop into C, write a user module, and get the benefit of easier Python syntax and C performance.

The only reason some hardware features aren't supported is a lack of effort to expose those features. Come help us fill in the gaps! :P

[1] https://www.youtube.com/watch?v=437CZBnK8vI (Not my best presentation, I'm sorry; I was running on very little sleep and a high degree of stress!)