Are CSS reset always needed?

CSS resets are based on three premises:

• There are differences in how user agents present web pages, that is, their default styles vary.
• These differences have an effect on the given website.
• The differences are important to be handled.

But there are developers that does not use these resets

• That there are sites and apps out there that do not use and that work fine without a CSS reset is pretty much never being talked about in the context of CSS resets.
• When we take the extreme positions of always and never needing a CSS reset, positions we observe in practice, then we end up with a contradiction. P & ¬P