There are different elements to different SSL certificates. An SSL certificate provides encryption between client and server. They all do this some at higher encryption levels than others.
However some CAs also provide the certs which allow for company name to be present which requires a few more checks by the CA. Then there are the EV certs which require the CA to verify the legitimasy of the company. These are all extras on top of the actual SSL cert function.
The same way that you provide differing levels of service levels for hosting. In essence it is just selling space on a disk drive and the sooner people recognise that the better
However I also agree that an SSL is not the defining factor in trusting a company with your e-commerce business. I have been in organisations that have an EV certificate on their store but when someone pays by credit card the details are emailed (yes emailed) to a lady who prints them off and taps them into a PDQ machine then files the print off in a filing cabinet in an open office! They really didn't think they were doing anything wrong or breaching any regulations.