My mum was a bit like this, back in the day.
Growing up, we were never poor (big inheritances from grandparents and parents came in quite early), but I always found mum's spending a bit odd.
For instance, fruit and veg always came from the market, in order to save money, yet she'd do all the rest of the food shop at Waitrose, when there was a Tesco and a Somerfield in equal distance.
She's always been really careful with everything she acquires. For instance, plastic bags were always carefully folded up and saved. Spread containers always washed out, and she'd see if she could repurpose them, before throwing them away.
Even now, she's frugal. For instance, it would never even cross her mind to nip out for a coffee, just for fun, "but I've got coffee at home".
I think a lot of people just mindlessly spend, out of boredom. My mum's just never been like that. If she's bored she'll sit with her book, or a puzzle, or go and potter in the garden. She'd never, ever, ever go shopping for fun! It honestly would never cross her mind.