The key insight and definition of a data lake was pulling data and storing in it's raw form form across the enterprise.

https://en.wikipedia.org/wiki/Data_lake

The reasons for it are hard to explain succinctly in HN comment but if you look up data lake there will be a lot of explanation. But it basically comes down to "is it better for the data integrators or the data consumers to massage the data?" And data lakes was the insight it's really great when the consumers decide how to massage the data.