Definition of 'Done' as Scrum teams mature

Hi All,

I thought an interesting topic for discussion would be about the definition of 'Done'. It is said in the Scrum guide that:

'As Scrum Teams mature, it is expected that their definitions of “Done” will expand to include more stringent criteria for higher quality'

Why is this the case? Shouldn't this be an expectation right from the beginning as the aim is to provide potentially useable functionalities which are appropriate, useful and competitive.