Well if you look at it that way, it is no difference than hitting a lucky return that also dribbles off the net.
If you ever played competetive tennis you will know that hitting a let serve is way more frequent than hitting a return let. If you have a good serve and often hit it just milimeters over the net, let cords will happen quite often.
In my mug carrer for example, I would hit some 10 let serves before 1 let return. Let returns are very rare in fact...unless you have a great day
Or just look at the pro matches - you see a let serve almost every service game, sometimes even 2 in a row (or 3 in a row in extereme cases), while let returns happen only a few times.
: Yes, I'm a girl. Profile pic is me. I watch and play tennis since 13 (1997). I don't play ITFs anymore, I have a job now. MTF-> uncovering my naughty side since 2007.
Slovenia's finest: Grega Žemlja, Aljaž Bedene*, Blaž Kavčič; Anže Kopitar, Goran Dragič, Tina Maze, PETER PREVC
WTA tour: Association of screaming tennis players without variety and defensive skills.
Kyrgios is an annoying mix of clown, punk and attention whore.