Including carbs as part of a healthy lifestyle can have different benefits depending on your goals. And here we are not talking about cheat days but an intentional inclusion of carbs on our lifestyle. We will talk of have we can do it further down.

• Have a diverse microbiome. Your gut microbiome is a very diverse and complex environment where trillions of microbes live in. When cutting groups of foods for a long period of time, you starve the microbes that live from that food. This will probably mean that if you try to re-introduce some of these foods you might not be able to digest it. Keeping this diversity is probably a good strategy for the long term.
• Support your fitness goals. You might want to include carbs on the days where you train hard, since exercising to induce hypertrophy and to an 80%+ of your VO2 max will require some glucose.
• Avoid physiological insulin resistance (glucose sparring). As you already know, it can happen that after long periods of time your body gets so used to ketones as the main source of energy where cells don’t know how to handle glucose. Although this is not a dangerous state as insulin levels should be low and controlled, but there is no reason to have more glucose circulating in blood than you need to.
• Have meal variety. Knowing how to get your nutrients also some times from a carb (or plant) source can be a good option, especially if you happen to be in a place which doesn’t serve what you are usually used to eating. Additionally, maybe you are the type of person that wants some variety and doesn’t want to have meat every-day. In this cases you should have a back-up plan