Like most problems in life, we'd like to think there's a single or at least primary culprit for "lost and wounded deer". Blaming the bullet is an easy way out. Not too hard on the shooter. I'd probably go with a top 3 reasons as:

1) lack of understanding
2) poor execution
3) poor shot selection

"Lack of understanding" likely leads the pack because knowledge not acquired through experience is frequently incomplete or misapplied and explains a wide variety of causes. A new ML hunter watching a "pro hunter" take a pronghorn @ 200 yards on OLN tries a long shot he's never practiced and hits but loses a deer. A ML hunter looking for an easier loading bullet finds that Powerbelts satisfy the need and shoot accurately but loads 3 - 50 grain pellets because the literature he got with his gun says it will handle "magnum" loads. Bullet fragments; lost deer. Hunter takes 75 yard shot from tree stand over thick understory, deer runs away; hunter thinks he missed and never goes to look or goes to look and never gets to where the deer stood when the shot was taken. Thinks he missed, deer lost.

Poor execution is simple lack of practice or buck/doe fever. The two are intertwined and if the latter precedes the former can become difficult to reverse or overcome.

Poor shot selection generally involes both of the above as the hunter over estimates the killing power of his bullet or underestimates the resilience of flesh and bone (lack of understanding) but only after the approaching animal has stopped and the hunter believes the opportunity is about to be gone so takes a frontal shot. No exit hole and deer is lost.

The great thing about forums, and this one in particular, is the ability to learn from others who have gained their knowledge through experience and present comprehensive explanations by the conversational nature of a forum. It's a special place.

My 2 cents...