I know people who say if they don’t have somewhere to go, they have no motivation to ride. These people may not regularly go riding for the sake of the ride itself, but are happy to ride to special events and are perhaps even regular commuters.
For those who need a reason to ride, I say do more errands by bike. If you schedule the commuting time in, which I generally consider double the time it would take by car, you may be able to do many errands by bike with the proper set-up. Grocery shopping? You might need to go a little more often and not get so much at once, but if you have the right panniers and backback, or maybe a trailer, you can make a destination ride out of it.
I know some cyclists who jump at the chance to get a missing ingredient for dinner, because it means a quick ride to the store. Too many time compromises in your life? Take the long-cut home. It de-stresses and gives some alone time. Don’t feel guilty about it. You need it for your well-being. I admit going to the farthest away grocery store or shopping in a completely different part of town I’d never drive to, just for the ride. It’s not difficult to get 20 mile rides in if you adhere to this strategy. Some do the bus-bike combo to work. If it’s a beautiful day, why not ride all the way home? You can makes some stops on the way. Some may need to take a change of clothes along, but really, it’s not a big deal if you plan ahead.
It comes down to habit, for the most part. What would happen if you limited car usage to transporting un-bikeable (are they?) kids, or trips to the home improvement/furniture store? I did manage a trip to the home improvement store today, but that was possible because the lumber was small and fit, with a little tying down with bungees, on my rack and panniers. I consider it a challenge to be met with ingenuity.
Doctor and Dentist? I bike. To the recycling center? I bike, and try not to let it pile up too much. Take the dog to the dog park? Use a trailer, or a small dog can go in a backpack or pannier. I’ve done it. Our old kiddie trailer is almost 30 years old, but is still fine for these tasks. It turns your bike into a station wagon.
Otherwise, if hauling a load, remember it may take a little longer, and you may want to adjust your route, avoiding big hills unless you enjoy the challenge. A simple trip to the store can become the reason you were looking for to get on your bike.