One reason to make your own butter is that you get distinctly different flavours depending on the type of cream you use.
If you use fresh cream you get sweet butter which is popular in North America, Australia and Britain, but less easy to come by in continental Europe. If you use a cultured cream like Crème fraîche you get cultured butter, which is common throughout most of Europe.
Cultured butter is slightly soured by lactic acid. It has a fuller, more complex flavour than sweet butter. If you decide to make it, be sure that you don't use a cultured cream that includes artificial thickeners. The ingredient list should read something like "pasteurised cream, lactic-acid culture" (apologies if that's not accurate; I'm translating from Swedish).
I have a couple of other reasons why I personally want to make butter. First of all my four year old son has been asking how butter is made, and this would be a great way show him. The second reason is that I'm curious as to how real buttermilk tastes (the buttermilk in the supermarkets is fermented milk). And last of all, I noticed that my beurre noir sauce was working out much better when I lived in Australia, so I'd like to do some side-by-side comparisons with European butter.
There is no such thing as "lower quality cream" although there are variations in taste.
All milk has a slightly different water to fat ratio. In general, animal milk is 80% water, 5% protein and 5% fat.
Cream is the fatty part of milk skimmed off. Cream will typically be 35% fat (though in different cultures it varies from 20% to 75%). Cream also has some protein, and the rest being water
Farmers are paid for the milk solids (protein and fat), not by the volume of milk produced. Therefore quality milk is often referred to by how high the solids level is, not how flavoursome it is. Hygiene and storage conditions are usually government mandated, and follow international guidelines, especially if the manufacturer ever wants to export the product
Butter is cream churned to remove most of the water and protein. Butter in most countries must have 80% or more fat content to be called butter. The water and protein by-product is called whey, and is processed into other products
The 1% to 2% salt added is a preservative and a commonly desired flavouring, regardless of the "quality" of the cream.
You can buy unsalted butter, just keep it in the freezer for long term storage. Freezing butter has no noticeable effect on it.
Best Answer
It means the butter is made from cream that hasn't been fermented. Butter made from fermented cream is known as "cultured cream butter", and it has distinct sour, lactic acid notes. Sweet cream butter tastes, well, sweet, and if it is from really good fresh milk you may be able to taste grassy notes. Both are good in their own way.