Crate training is also necessary when certain circumstances require management. The most important for frenchies is the the risk of spine issues. If the need arises for a 6 week strict crate stint - which is mandatory to allow for a herniation to heal- you don't want to be in that situation with a frenchie who does not like or want to be crated. Similarly other medical situations may require that you dog be safely contained especially when you are not around at home as well as at a vet's clinic or in a boarding facility.
There will be other situations like houseguests during holidays or you may want to consider fostering and want to be able to separate the family dog from the new lodger temporarily - ie where risk of unwanted behavioral issues can be better managed by crating. A crate is also a great way to transport your dog in a vehicle. Crating should therefore be 'practised' to a certain extent and certainly not forgotten after puppyhood, to ensure it can always be used as a management tool.
In all these situations, your dog should be willing to go to it's crate and been trained to rest, sleep or spend time with a kong in there without complaint.
See Crate Training 101 for the best ways to teach your dog how to like and enjoy being in his crate. See the videos for some more nuanced training which might be helpful if you are having a problem and might need to know how smaller steps in the process will help to get you back on track.
An open metal frame crate is best for a frenchie to avoid the risk of overheating in a more enclosed container.
Once housebroken and reasonably trained to spend time alone and reasonably past juvenile destructive behaviors - a behaviorally healthy dog should be able to spend time alone in a limited area of your home without the need of a locked crate. Crating should not become a 'lifestyle' where the dog spends many hours a day locked in one. Excessive crating can contribute to problem behaviors see :
Crates, a good thing gone bad,
To crate or not to crate
Should I crate train my dog?
