帮我看下这个被动句,理解不了···

帮我看下这个被动句,理解不了···
few things could be more impressive than the peace that descends on deserted city streets at weekends when the thousands that travel to work everyday are tucked away in their homes in the country.
周末,当成千上万的进城上班的人回到了他们的乡间公寓后,空旷的街市笼罩这一种宁静的气氛,没有什么比这时的宁静更令人难忘了
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我不能理解的是为什么是are tucked away ···
而不是tucked away
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