Why when using composable function inside watch store = undefined?

Question

Vue.js

Hello. There is a component with composition api.

<script setup>
import { computed, ref, watch } from 'vue';
import { useStore } from 'vuex';
import useAvailableChestChampsData from '@/composables/useAvailableChestChampsData';

const championsWithChests = ref({});
const store = useStore();

const allChampionsAvatarsURLS = computed(() => store.getters['imagesStore/allChampionsAvatarsURLS']);
const foundedUser = computed(() => store.getters['currentUserStore/currentUserHeaderData']);

watch(() => foundedUser.value, (newUser) => {
  (async () => {
    const { availableChestChampsData } = await useAvailableChestChampsData(newUser.id);

    championsWithChests.value = availableChestChampsData.value;
  })();
});

</script>

In it, I use the composable function.

import { useStore } from 'vuex';
import { computed, ref } from 'vue';
import api from '@/api/api';

const useAvailableChestChampsData = async (userID) => {
  const store = useStore();
  console.log(store); // Почему store = undefined???
  const championMasteries = ref([]);
  try {
    const { data } = await api.user.allChampionMasteries(userID);
    championMasteries.value = data;
  } catch (e) {
    console.dir('Не удалось получить информацию о героях пользователя', e);
  }

  const allChampionsStore = computed(() => store.getters['handbookStore/allChampions']);

  const availableChestIdArr = computed(() => championMasteries.value.reduce((acc, champion) => {
    if (!champion.chestGranted) acc.push(champion.championId);
    return acc;
  }, []));

  const availableChestChampsData = computed(() => Object.values(allChampionsStore.value)
    .filter((champion) => availableChestIdArr.value.includes(Number(champion.key))));

  return {
    availableChestChampsData,
  };
};

export default useAvailableChestChampsData;

But for some reason, when the watch trigger and the useAvailableChestChampsData function fires, the store, which I declare inside it through useStore = undefined. That is, there is not even a vuex instance, let alone data.

Thanks in advance