Actually what happens is if you set Enabled = false
for some ASP control, that particular control will rendered on client-side but its class will be set as "aspNetDisabled"
which prevents its value to be edited. I found no way to edit/change this class. So, you can't edit its value using any client-side script like JavaScript.
When you try to post its value back to server, the initial value is used which was there in server.
If you enable the control, it gets rendered and in that case you can access/edit its value as you want.