I've had the opportunity to work at quite a few start-ups. One thing I've found to be common in them is adhoc way of doing things and ignorance towards processes, best practices and known project management techniques. When I suggest changes to the employers they come up with the answer that all these processes look good in books and reality is different OR they are only relevant in Google, Microsoft and Yahoo like companies.

For example in the middle of the sprint (in Scrum) a product owner would come and say. Hey I've changed my mind about so and so feature so lets do the changes. Don't tell me about man hours, estimates and sprints. Just finish this tonight.

It seems start-ups are exempted from following the standards and best way for them is to just go with the flow and make decisions based on gut feelings. Is that true? What is the justification?