And some people will cook more. For example, we have a lovely little neopolitan pizza joint a block away, but two days ago I received an Ooni Koda 16 and have discovered how easy it is to make my own neopolitan pizzas. That's basically a permanent reduction in my spending on pizza if/when it does reopen.
My guess is when you're tired and just want dinner now-ish, you'll learn to value that nearby restaurant. It's not like restaurants are only viable because people don't know how to cook themselves.
You can quibble about a specific food, but I think the general point stands. Habits are powerful and they can change. Every adult in the country (world?) is now forcibly learning how to cook or practicing a few new recipes. It turns out that some of those recipes are delicious, dead simple and once you know how to do it, having someone else do it for you looses it's convenience factor.
For myself:
I love cappuccino and bought several per week from cafes near me. I was missing them, so did a bit of research into home espresso and bought a nespresso and semi-automatic milk frother. My homemade cappuccino is excellent. It takes 2 minutes to make with just about zero cleanup. I have had better cappuccino, but seriously the extra time, money and hassle are no longer worth it for me. I will make it at home. It's also 6x cheaper.
I like to treat myself to steak every now and then, but only ever at a restaurant. I recently bought a package of strip steaks and did some trial and error on a George Foreman grill I found in the back of the cupboard I hadn't used in years. I figured out a process that works with that piece of equipment, and now I can knock out an amazing steak in exactly 4 minutes. It's cooked exactly how I like it. Why bother with the hassle and expense of going out for one? Plus it's 4x cheaper.
I doubt I'll completely stop going out or getting delivery, but if I reduce by 10% and everybody else does too, we're talking a lot of businesses that will close.
I'll do you one better on the steaks. Buy a Beville Joule and a vacuum sealer. Season the steaks with salt and pepper and vacuum seal it. Heat with the sous vide to 110F for a 1" thick ribeye. 120F for a 1.5" cut. Preheat grill to 500-600F. Remove steak from water and bag, pat dry and re-season (most of the original season was absorbed into the steak). Then toss on the grill for 1-2 minutes each side depending if you like it done rarer or better cooked.
Adjust accordingly to your liking, but in general, you can easily achieve premium steakhouse quality with this approach with 30 min to 1 hour, start to finish. Mostly the sous vide as used here is about bringing the internal temperature up so that the steak cooks quickly and more evenly than a steak pulled right out of the fridge. This is even less cleanup than a foreman since the only thing getting dirty is the surface you season on (usually the paper the steak is wrapped in) and the grill you just need to brush with a wire scraper.
I recommend a VacMaster VP215, but I understand if that's way outside your budget. I personally use mine daily for lots of things besides sous vide like storing food, saving sauces
Supporting example: WE are making bubble teas with boba at home, takes about 10 mins and they are amazing and much cheaper and convenient than $5-6 that bubble tea places here charge.
Counter example: We basically rarely ordered delivery and preferred take-outs. However, due to the increased delivery usage recently we figured that since delivery costs are similar for a restaurant 5 miles or 15 miles out, we are getting food from restaurants further out than we would normally not go to as they were too much of a drive.
