You have been lucky! We have looked at renting some really pretty ones - then checked reviews and found that there was no wifi. So went back and did a hasty check on the cottage info. Thank heavens. Now we are a lot more careful. We were seconds away from booking one up. As 19 yr-old DS is coming with us it would have been dreadful! We would have had to play board games... we do still play them when all the family is together but I would rather read if no wifi is available, just never allowed to. We used to rent National Trust cottages, which are stunning, but only recently have ONLY a few cottages had wifi installed. If you are somewhere remote and can't get phone signal either, you are stuffed as many properties do not have a land phone. In fact some can barely get TV reception.
In France it's even scarcer. The flats in Paris are generally fine, as you would expect, but once you get outside it's a different matter. In fact although I really wanted to rent a french cottage, generally the ones owned by Brits are better equipped. Small hotels and B&Bs usually have wifi though for their business.