Except when it doesn't. I'm facing this problem with an embedded-ish project I'm working on where Python initially seemed like a good choice, but now we're regretting it for both performance and power usage reasons. If we'd gone with C or C++ initially we'd be having a much easier time optimizing.

Not that I'm implying Python is bad, but if your target use case doesn't allow for a desktop or server, think carefully about what tech you use.