Anyone know why the pin 10 never goes high, when using the other SPI devices?
Why would it? Your snippet doesn't access pin 10. Pin 10 does whatever the rest of your code told it to do.
On the AVR Arduinos, pin 10 must be an output when using SPI as a master. If it's an input, the SPI system goes into slave mode and waits for that pin to go low. But as a master, you can control pin 10 to do whatever you want. It's just another pin.