The phrase "practical necessity" means something that is needed or essential in a practical way. It refers to things that are required or important for everyday tasks and situations. Full definition
Bathing your dog can be a wonderful bonding experience but it's also a very practical necessity for our sometimes smelly canine friends. (lovethatpet.com)
This was especially common in the days when research was primarily done with books, as a matter of practical necessity in controlling size and expense, but it's still used by many US state courts to filter which decisions become precedent. (law.stackexchange.com)
Alternately many younger parents particularly appreciate the unique place of parents in the AP framework, when they are often forced by practical necessity to depend on grandparents and other family members for «co-parenting» support. (attachmentparenting.org)