I work in loss prevention so seen it all.
It does vary by location but there are many food banks, charities and Safeguarding services that support with food, baby milk, hot meals, toiletries.
I very rarely stop someone who has stolen essential items that they genuinely can't access elsewhere. On the rare occasions that's happened they are safeguarded & referred to appropriate agencies.
Some do it for the 'thrill' some do it because they believe they have some sort of entitlement & supermarkets have more money than them. Some do it because they want things they can't afford.
Buying to sell on for drugs or drug debts is also common, or alcoholics stealing alcohol.
There are also criminal gangs which steal to order large quantities of products such as baby care, chocolate or cleaning products that are then sold on to independent 'mini marts' across Europe.
Yes supermarkets do a lot to deter & disrupt criminal activity & work together with other retailers & police & national crime agency to tackle the most prolific offenders.