The tasks are fascinating and, looked at from a business viewpoint, often amazingly hard. To dream up new products, get them designed and then sell them to professional buyers, (to take one example), compresses a normal business process that might last months into a couple of days. And they have the cameras on them the whole time.
I find the earlier shows much more interesting than the final stages. It is the way that the teams organise themselves and how they build on their strengths, as well as trying to do each other down as individuals, that makes it compulsive watching.