Why do some Realtor not even acknowledge offers?

[Ryan Dossey]

I'm starting to run into this more and more. I don't know if it's laziness, they're busy, or just plain inconsiderate. If I have a listing and someone makes an offer on it... Even a low offer... I'm thanking them for their time. Letting them know that I will show it to my clients and they should expect to hear back shortly. 

We offered 8k under a list price with cash. Large EMD. No contingency other than 3 days to walk my contractors through it.

Not so much as an acknowledgment of reception.