plenty of budget phone SoCs use small core clusters only
I'd say that the mainstream segment below high end is mostly SoC's using older generation 'big' Axx cores, so basically SoC's with 2-3 gen old cores on a newer node.
Below that pretty much all truly budget phone SoC's use only little cores.
Though even in mainstream and high end/flagship phones the little cores are still very important.
Anything that doesn't require a heavy compute load and/or background apps running while the phone display is off are going to be running on those cores.
So they actually play a pretty big part in the general efficiency of a SoC for a battery powered mobile device, and next to radio power draw they will probably play the biggest part in battery life.
While radios currently eat so battery much that this is less significant, the coming advent of 'passive' wireless tech will put the efficieny ball much more in the court of the little cores.
Not to mention they are used in basically 90+% of all streaming devices like Fire TV, Chromecast, Roku etc etc which is no small market by itself, and likely way more than half of all STB and TV SoC's too.
Sadly streamers seem to be very slow to get new upgrades, I think the first to get A55 was the latest Chromecast 4 that came last October, nearly three and a half years after the core IP was announced in 2017 along with A75.
Going by that we'll probably see A510 in streamers late 2024 😅🤣