Why iOS developers don't write unit tests

"The majority of responses fell into this category; lots of developers don’t see the benefit of writing unit tests or even believe they’re harmful."

If the majority see no benefit, how do you come up with "a lot of people said they should write tests but either don’t know how or don’t feel like they have enough time."

In a response cohort of 30 I doubt you have much to go on, but consider that in practice, formal code reviews, baseline acceptance testing and large scale beta testing are far easier to manage and are far more useful for finding issues. I personally have experienced that often testing is harder and more time consuming that the actual code. The benefit is marginal at best. Testing code is objectively MORE code to maintain and debug.

Personally I have found that structuring my code so that I am able to write unit tests has been far more useful than any unit tests themselves. For your code to be testable it requires a certain structure and decoupling of dependencies that was not natural to me at all when I first starting doing projects. Now that I know that I might one day want to write a suite of tests with full coverage, I write my code much differently.