Scalability is not a feature. If you "need" to scale but don't then you're not delivering to your target market, not delivering is not a lack of a feature it's a net loss to the organization. If you're Twitter/Instagram/Uber/whatever you cannot tell your users to not post or like or request a ride because "right now we don't have the scalability feature"
Yes, if you can't scale fast enough as you need to, it can hurt your business. Not being able to keep up with demand is a (luxury) problem that every business faces, not just in tech. They would often be called 'growing pains' in a business, and though they are bad, they rarely contribute to the failure of a company.
Starting a startup/service/platform with microservices before you even understand the bottlenecks/market fit/customers is usually not a good idea. You can come a very, very long way with a monolith before you hit performance and scalability limits. And once you do, you can always start breaking things up into smaller services for scalabity. Obviously you need to make sure you are scaling on time to keep up with demand.
'Nail it, then scale it', and 'premature optimization is the mother of all f-ups' are popular sayings for a reason.
I'm not making a case in favor of starting with microservices for your startup, that'd be insane, to say the least. I'm just disagreeing with "scalability is a feature". A feature is every addition on top of your minimum viable product. If at some point it becomes apparent that the business needs scalability, then scalability becomes your minimum viable product.
