As Legio was responding and piggy-backing off my points, I'd like to answer.
Many of the industries which employ workers for under $15 an hour have had serious financial difficulties due to pandemic (such as hospitality and restaurants).
One out of six restaurants in the US have closed due to the pandemic, and the surviving restaurants are just barely getting by trying to pay off rent and taxes. Take-out hasn't been effective at recouping lost revenue, and I suspect that many people will likely remain hesitant to go out to eat even when the pandemic subsides; if there is one clear result of the pandemic, it is the fact that authority figures have induced a culture of anxiety and trauma (whether this is justified or not belongs in the main COVID thread) which has scared people from participating in public life.
Suddenly forcing restaurants to hike up their wages might tip many of the remaining businesses over the edge, putting them out of business. Naturally,
doubling the minimum wage when low-wage industries are already suffering will further contribute to the economic downturn and mass-unemployment as both employers and their employees are forced onto the street because the cost of business has increased beyond their means of acquiring revenue, meaning that even more people are left jostling for even fewer jobs.
Restaurants are only one aspect, but they are a significant part of America's culture and economy. I can't find a specific source, but this
infographic suggests that restaurants contribute 4% of the US GDP and employ almost 10% of Americans; they also serve as the first job for many young Americans, and we can say that they are a formative part of the career development for many Americans. Although many people in my (millennial) generation want the $15 wage, few know how badly this will hurt them when that these measures can and will hurt their employment prospects when it affects the very industry where most of us work -- at a time when we've already been kicked in the nuts by a pandemic-induced economic and societal crash.
Overall, I'm not opposed to a $15 minimum wage at some point, especially considering the rate of inflation. However, forcing a wage increase during an economic downturn does not help the economic recovery and does not help the United States recoup lost jobs. It is better to have a job that pays little, than no work to find at all.