“They probably left over price.”
“If they wanted us, they’d call.”
“They must be happy with whoever they use now.”
“They never complained, so nothing was wrong.”
“We already know why they left.”
Any of those things may be true.
I wouldn’t assume they are.
People often leave quietly.
They don’t always complain.
And the explanation written in an account record may not be the explanation the customer would give if the owner called and asked.
That’s one reason I prefer conversation to assumption.
You may learn there is no opportunity.
You may recover the relationship.
Or you may discover a problem affecting other clients who haven’t left yet.
All three answers are more useful than guessing.