Simple: they're not venture-backed so no one is expecting billions from them.
23andMe could be a longer-term sustainable business but taking $700m from investors means you must keep growing even if there's no really opportunity for growth.
driving schools likely have far more customers, a constant influx of customers based on age, and driving (in the US at least) is a necessity, and thus supplies the market. I'm also just spit-balling here: the cost of a tech company's upkeep is FAR MORE than that of a driving school's
