[lucozade]

Because they are good ideas if you want your CPU to run fast.

The combination of features involved: caching, branch prediction and out of order execution are all very valuable. Both individually and in combination.

What has been discovered is that, under certain circumstances, they combine in ways that can leak sensitive information. This is a very bad thing and needs mitigation/fixing.

However, it doesn't mean that the underlying features are inherently bad. Just that they have complex interactions that aren't as well understood as, perhaps, was thought.

When this all settles down, I wouldn't expect these features to be removed. Rather they will be constrained such that they retain as much performance as possible but without the security implications.