Windscreen broken

Travelled on a Tui flight recently when the windscreen spider cracked and caused plane to be diverted back to uk when over France travelling south.Does this happen often and why did they turn back as they said ‘nothing to worry about, just routine’

@Capellania650 This does happen on some flights, recently it did happen on a southwest jet which was diverted and also on an AirIndia 787 dreamliner, they mention “NOTHING TO WORRY” on PA to keep the passengers calm and they divert as a precaution as this small window break can also be a sign of much larger issue with the airframe.