In a word, yes. Vehicles are more likely to be stolen if they are parked in an insecure place overnight, such as on the street or a driveway, and insurers take this into account when assessing the cost of insurance premiums.
Therefore if you have a garage you are using for storage rather than parking, it could save you a lot of money if you cleared it out and parked your car inside instead.
However, if you have told your insurer that you park your car in a garage overnight, it is in your interest to ensure that you do, as if your car is stolen while it was parked elsewhere, depending on the circumstances, some insurers may consider your policy void, while others may charge you charge a higher excess.
For people who alternate where they park their car, for example, sometimes parking it in their garage and sometimes parking it on their driveway, it is a little more complicated. In such an instance, it is generally advised that you state you park your car on the driveway, as you will be provided with greater cover and your chances of a payout are also increased.