It’s never really explained in so many words, but there is still an oblique explanation

 It’s never really explained in so many words, but there is still an oblique explanation. Her song, ‘Grizabella: The Glamour Cat’, is quite dense in its language - and was removed from the original collection of poems the show is based on since TS Elliot thought it was too depressing - but the basics of it is that she was once the talk of the town (so essentially the female equivalent of Bustopher Jones) but then essentially did the feline equivalent of blowing all her money on booze and drugs and winding up as a prostitute (yes really); so…I guess overdosing on catnip and snuggling up to different families/tomcats for affection, potentially including Macavity (which is the explanation the movie chooses to go with). But in the end, the “why” really doesn’t matter very much. All that’s important is that she’s not welcome until the very end.

https://gnomiestore.com/shop/saul-goodman-2024-perfection-is-the-enemy-of-perfectly-adequate-shirt/
https://gnomiestore.com/shop/santa-its-hot-as-balls-of-holly-out-here-shirt/
https://gnomiestore.com/shop/roses-are-red-doritos-are-savory-the-u-s-prison-system-is-legalized-slavery-shirt/
https://gnomiestore.com/shop/ron-swanson-2024-i-regret-nothing-the-end-shirt/
https://gnomiestore.com/shop/ron-burgundy-2024-you-stay-classy-america-shirt/
https://gnomiestore.com/shop/rodney-what-do-you-think-i-am-some-sort-of-wally-shirt/
https://gnomiestore.com/shop/rip-biz-markie-1964-2021-shirt/
https://gnomiestore.com/shop/ricky-bobby-cal-naughton-jr-2024-if-youre-not-first-youre-last-shirt/
https://gnomiestore.com/shop/respect-369-wins-60-shutouts-1-goal-fang-fingers-so-nashville-shirt/
https://gnomiestore.com/shop/reagan-bush-84-shirt/
https://gnomiestore.com/shop/ray-finkle-2024-laces-out-shirt/
https://gnomiestore.com/shop/randy-watson-2024-i-believe-the-children-are-our-future-shirt/
https://gnomiestore.com/shop/puck-multiple-sclerosis-lets-crush-ms-shirt/
https://gnomiestore.com/shop/potter-weasley-2024-shirt/
https://gnomiestore.com/shop/pineapple-slut-shirt/
https://gnomiestore.com/shop/peyote-pepsi-shirt/
https://gnomiestore.com/shop/pedro-napoleon-2024-vote-for-me-and-all-your-wildest-dreams-will-come-true-shirt/
https://gnomiestore.com/shop/peaceful-protester-text-trump-to-88022-shirt-2/
https://gnomiestore.com/shop/pac-biggie-2024-cant-we-all-just-get-along-shirt/
https://gnomiestore.com/shop/omar-little-2024-you-come-at-the-king-you-best-not-miss-shirt/