Why v-slider (Vuetify) has no width?

I want to create a v-slider, but just on default empty v-slider tag has no width or thumb align center:

This bold point is the thumb of slider and no one slider bar.

<div v-if="typeList[0] === 'grade'" class="formItem__grade">
    <v-radio-group v-model="item.value" inline>
         <v-radio v-for="el in item.meta.answers" :label="el" :value="el" :disabled="disable"></v-radio>
    </v-radio-group>
    <!-- 
    <v-slider v-model:model-value="item.value"
        :ticks="item.meta.answers"
        :max="item.meta.answers.length"
        show-ticks="always"
        step="1"
        tick-size="3"
    ></v-slider>
    -->
    <v-slider></v-slider>
</div>

In the commented code, you can see that I tried to set props, but it did not work. So I tried <v-slider> without any props (as in the image), but it does not work either.

That happens when you don't wrap you Vuetify components into a v-app. It works when you do:

<!-- begin snippet: js hide: false console: false babel: false -->

<!-- language: lang-js -->

const { createApp, ref } = Vue;
const { createVuetify} = Vuetify

const vuetify = createVuetify()
const App = {
  setup() {
    return {
      sliderVal1: ref(25),
      sliderVal2: ref(1), 
      item: {meta: {
        answers: ['a1', 'a2']
      }},
      isVapp: ref(true)
    }
  }
}

const app = createApp(App)
app.use(vuetify).mount('#app')

<!-- language: lang-html -->

<link rel="stylesheet" type="text/css" href="https://cdn.jsdelivr.net/npm/vuetify@3.1.6/dist/vuetify.min.css" />
<div id="app">

  <label><input type="checkbox" v-model="isVapp"/> with v-app</label>
  
  <component :is="isVapp ? 'VApp' : 'div'">
    <div>
      <v-slider v-model="sliderVal1" />
    </div>
    {{sliderVal1}}
    <div>
      <v-slider
        v-model="sliderVal2" 
        :ticks="Object.fromEntries(Object.entries(item.meta.answers))" 
        :max="item.meta.answers.length - 1" 
        show-ticks="always" 
        step="1" 
        tick-size="3" 
        color="blue"
      />
    </div>

    {{sliderVal2}}
    
  </component>
</div>
<script src="https://unpkg.com/vue@3/dist/vue.global.prod.js"></script>
<script src="https://cdn.jsdelivr.net/npm/vuetify@3.1.6/dist/vuetify.min.js"></script>

<!-- end snippet -->