I believe Alibaba is either a scam or a company that focuses primarily on spam. I recommend avoiding it at all costs.
I can only assume you have had a bad experience with a supplier that you met there in the past.
Here's my take on it:
Alibaba is no scam, they don't actually sell anything beyond advertising space and financial services to their advertisers, which as a buyer, you don't pay for. It's merely a trade portal for business to business. It is no different really to any other trade portal with access to worldwide markets, there are many suppliers advertising there from all over the world, not just those based in China. Just like any other trading portal, the Alibaba service will, if you have either signed up for it, or not opted out of it, email you lists of new items and suppliers, based on the results of your previous searches of the site. Ebay, Paypal or the Chinese based TaoBao focusing on the private individual is no different in this regard, just about everyone and his mate these days has at least a news letter opt-in/ out when you sign up for their service. It's not really spam if you agreed to receive it. It is usually easy enough to set your account preferences such that you don't receive the emails.
Of course Alibaba is primarily focused on business customers as are the other trade portals, so the larger companies advertising there may be reluctant to deal with you for a one off item, especially if you present to them as a private individual. That policy however is no different to that found anywhere else in the world. Suppliers advertising with the various trade portals are not retailers like mouser or digikey, they are large distributors and manufacturers and they are not geared up for retail sales, even if they do agree to the odd one here and there. None of them are going to chase you down for a $10 sale, so it's up to you to make contact with them directly. Call them or find a sales contact's details from the company profile and skype them or email them directly. Either way, if you strike up a little dialogue most are usually more than happy to help you, or if they can't, at least inform you where you can obtain the item as a one off.
Making contacts and developing new business with Chinese suppliers can be fun and rewarding. The Alibaba/ AliExpress services are generally very good in my opinion at providing a platform of common interest. Obviously, just like any other supplier you buy from, due diligence should be carried out to ensure they are above board. Safe methods of payment should also be agreed between both parties for goods purchased. Keep in mind that suppliers also have a business to protect against fraudulent customers, of which there are plenty. Genuine suppliers advertising on Alibaba, or any of the many other trade portals for that matter, will be more than happy to work with you to achieve a good outcome, they want your business and you as a long term customer
The last thing to note if dealing with suppliers worldwide, you need to pay attention to local time. There's no point in trying to Skype someone in the middle of their night!