Jousting lances are, but lances used in war are not.
They're not designed to shatter on impact, though. And actually, historically in the 14th-16th centuries, they weren't "one use". Late medieval war-lances weren't the fancy curved-guard things we see used in jousting, by and large, they were basically just long, relatively thick-hafted spears and often tapered a fair bit.
They were not "one-use" most cases - you might well lose one in a charge, in which case you change to whatever backup weapons you had, or ride off and get another lance, but you don't like aim to lose them.
And they were absolutely built sturdily enough to survive a charge.