Not always, but you do get favourites - ones you know are great to deal with, have helpful BDM's, and good policy.
If he/she is putting ALL your loans with one lender, I'd be concerned as it's always better to spread them around a bit. A couple is fine, 3 or more (depending on situation/portfolio etc) and I'd be asking questions - they may have a perfectly good reason, but they'd want to be able to explain it thoroughly to you.