It is a really tricky subject and different hosts treat it differently. Generally you are absolutely correct - the loyal customers is what keeps the hosts afloat and they should be treated with the utmost respect and gratitude. So naturally, hosts should think of ways to express that. Renewal discounts, feature discounts that they will only see in their Client Area, giveaways and contests - there are quite a lot of options.
There is one thing I believe you are in the wrong tho - EasyHostMedia experienced it with his van insurance and the same type of thinking applies to many clients in the hosting business - discounts for new and existing customers. As you may well know, the bonuses for the loyal clients are somehow lower than the ones for new ones. Seems unfair, right? Well...to an extent. I actually believe this is quite justified. Here is why.
Lets say that you are a web host and (in your mind) provide a quality service at a good price (like most believe). Now - would you be able to sell accounts more easily to a person completely unfamiliar with your service, who just have to believe your words, or to one that is well aware how good your hosting and support is? That is the point of the introductory bonuses - giving a person who doesn't know you, a taste of your quality, an opportunity to test you for a longer time and not lose much. You should well know that often the prices for acquiring a new customer are ridiculously cheap, often cheaper than the real value of the package. And that is the cornerstone - knowing the real value of your packages and knowing how to back up that claim. Because if you give such low promos for both new and existing customers simply means that you will be disappearing after some time, unable to keep up with your bills. If your loyal customers really like you as a host they should well understand that, its basic Commerce 101.
That being said, again, I am all up for keeping loyal customers happy too. Its just that this does not necessarily be expressed with huge discounts. Keeping a great customer service, expanding, improving, innovating are just a few things that many people out there look for and will make them satisfied.