You close at 6 PM. Calls come in at 7 PM, 8 PM, 9 PM. People researching services for tomorrow. They call you, get voicemail. They call competitor, get answer, book appointment. You lose.
Your hours are on your website. On your Google listing. On your voicemail. People still call to ask. 10 to 15 times daily. Every call interrupts whatever you're doing.
Someone calls asking what time you open. You stop what you're doing, answer the phone, tell them your hours. Five minutes later, another call. Same question. This happens 15 times a day.
You're 15 minutes into a haircut. Phone rings. You can't answer without stopping mid-cut. You're doing a dental procedure. Phone rings. You definitely can't answer. Call goes to voicemail. Customer books elsewhere.