I always found the diversification by the supermarkets into car insurance, broadband and mobile phones distasteful. At least with mobiles, though, it was because customers were buying talk time in the store for other providers.<p>But streaming services is not where they should be. Tesco, in particular, has a poor security approach.<p>They even tried getting into the Used Car business but couldn't secure a supplier.<p>The problem for food sellers is that growth is constrained - they have managed to make plenty of people fat but even then, there is a limit.<p>The pressure to grow has ended up damaging Tesco but I doubt it will be much of a lesson to others.