When you buy in store, the old saying "bought as seen" applies. If I buy some food and find out on the way home that it's spoiled and past date, I can bring it back and likely it'll get replaced but they don't have to. I should have checked. When you buy glasses, check for scratches.
For warranty claims you'd need some kind of bigger problem than something that can be considered wear and tear or that was present when bought.
The consumer laws are concerned with malicious activity where someone is trying to actively trick a customer (which is where you get silly rulings like vegan sausages not being able to be called sausages as such would imply it contains meat).
And don't worry about implications or consequences, when the responsible government offices get riled up they really hit hard.
In regards to mobile/internet contracts, it helps to read the fineprint. Additionally if they do make trouble, contacting your local customer rights organization, the contract will get dropped very fast with little complaints.