Dark patterns are a short-term tradeoff. Ultimately, though your customers will resent you.
Its easy for stakeholders to say "So what? We loose a few customers!"
However, your company really might be loosing a potential investor, a potential business partner, a potential star hire or a potential product champion.
Ambitious companies don't use dark patterns but dying companies do.
I used to believe this - but once you reach a certain scale and number of users, they do not notice small things - especially if they are average everyday people.
We are all hyper-sensitive to design, functionality, behaviour because we build and make decisions about technology, but at the end of the day most people have 5-to-15 minutes to use your product during or between other work and conversations.
Investors will likely not be carefully analyzing your UI, unless they have a lot of time - most of their decision will be based on conversations with your top-level executive team and the information provided therein.
Star hires is a potential one - I can definitely imagine that a lot of very savvy designers and engineers might be put off by manipulative design decisions - but ultimately they may care more about the workplace environment that you claim as a company, the opportunity to be part of a growing business, etc.
I'm a touch on the pessimistic side with this one but these are my perceptions, partly based on experience and partly based on observing startup businesses evolve over time.
Its easy for stakeholders to say "So what? We loose a few customers!"
However, your company really might be loosing a potential investor, a potential business partner, a potential star hire or a potential product champion.
Ambitious companies don't use dark patterns but dying companies do.