Anna Hartley said bars were associated with a number of "risk factors" linked to the spread of the virus, but joked, "Your guess is as good as mine," when asked why exactly 10pm was the new closing time.
The curfew, which was announced by Boris Johnson on Tuesday and also applies to restaurants and other hospitality businesses, comes into effect on Thursday.
The government is yet to fully explain the thinking behind the move, but it has also delayed plans to allow sports fans to return to stadiums.
People are being advised to work from home again if they can.
The curfew was discussed on a live Q&A session hosted by Wakefield Council on Facebook on Tuesday, minutes after it was formally announced.
Asked why it was being brought in Ms Hartley said: "I think what we've learned about Covid is it's an inexact science.
"Some of the things we were told about it in January, by July they were no longer the case.
"We know that in pubs and clubs you have a lot of people together in a small space and they're drinking alcohol and potentially lowering their inhibitions.
"We know the virus spreads through droplets and people are sometimes having to shout over the noise of the music to each other, so there's significant risk factors there.
"Why is the cut off 10pm? Your guess is as good as mine! Do people drink more or shout more after 10pm? I don't know.
"Covid is an incredible challenge, and the decision making is incredibly challenging.
"I think some of it is about introducing an arbitrary cut-off in the hope it will reduce infections."
Back in May, several local pubs warned they would struggle to cover their losses if they had to reopen with strict social distancing measures in place.
A number of people across the hospitality service warned that the industry could be devastated by the new curfew.
The latest data available indicates Wakefield's infection rate stands at just above 27 people per 100,000 - the lowest in West Yorkshire.
Local Democracy Reporting Service