Your two questions actually go hand in hand I would say:

I think the reason you don’t see so much focus on working capital in start-ups is that the major household names that people see and know as success stories are funded my large amounts of venture capital and are often burning huge amounts of cash to get to that position.

Whereas the success stories that come from good, solid, working capital management are typically bootstrapped start-ups that fly more under the radar and create long-term sustainable businesses that just don’t become household names.

Typically, these companies are private and don’t disclose much in terms of numbers so it’s pretty tough to find big brand-name examples… but a good way to uncover some nice ones (that actually get some press) is to search for articles on the most successful crowd-funding campaigns. (Nice article here in the WSJ for example: https://www.wsj.com/articles/the-10-biggest-crowdfunding-campaigns-where-are-they-now-1525140660)

BUT what you will find, is that many of the largest campaigns by $ value, didn’t always lead to successful companies. Rather, the one’s that are most successful in the long-run use crowd-funding for working capital (scale up production) rather than for designing and launching unproven products from scratch.