I'm sure it was picked a long time ago and it's too costly to switch. I imagine any code going into multi-million dollar missile needs to be incredibly audited

I'm sure it was picked a long time ago and it's too costly to switch. I imagine any code going into multi-million dollar missile needs to be incredibly audited and understood. (Not that this never happens! https://www.simscale.com/blog/2017/12/nasa-mars-climate-orbiter-metric/ https://www.simscale.com/blog/2017/12/nasa-mars-climate-orbi...)