I think maybe coz you are to undervaluing the domains. Giving low offers sometimes makes the domain holder fell insulted. If you want you can pm me the domain and I can evaluate it for you. And also I'm not interested to buy it so don't worry. Take note if its crucial keywords domains you will need to offer or min low $500. I once wanted to buy a domain and offered less than $500 but the seller just deleted my mail.. lol..
lookup the whois information for the domain and call the phone number if listed. If you can get them on the phone you got a much better chance of letting them hear you out then emailing them
i never understood the concept of BUYING a domain name for... lots of cash... but I'd love to sell all 50 of mine for big-bucks each.!!!! You can always find a similar domain name.. and make it do what you want it to do.