I know, people here are demanding that after you fill up at an all you can eat buffet, you should be allowed to sell your seat to somebody else.
This is especially bad for the authors in case of content based product. If you are selling copies of knowledge you acquired then forcing you to allow reselling means you will have to sell for much higher price or not at all. There are opinions and verdicts of EU courts which makes different rules for content based electronic goods. For example you are not forced to grant refunds with those. I really hope Steam wins the appeal or that courts in other countries won't repeat this verdict (it's not case law in most of Europe so what French court decided hasn't much weight in Germany or Poland or whatever other country.