At least they sold it thinking it would work, and it probably did. You can see the physical evidence of shoddy workmanship in the box. But with firmware, shoddy workmanship is often hidden by the slap-dash programmers who hide their sloppiness. I once inherited and had to rewrite about 50,000 lines of shockingly bad firmware. Almost every line. A terrible experience for anyone who had not been sentenced to prison with hard labour.
DLINK sold a modem/router for about 2 years without some of its published functions working and their customer support was non-existent. The firmware was atrocious. I was a DLINK victim and after 18 months of toiling with the DLINK crap, I ended up I smashing it up into tiny pieces with a hammer and posting the debris in a box to DLINK Australia, addressed to the Managing Director with a one page descriptive note about what I thought of his DLINK company and his modem/router. Never touched DLINK since and never will. They are black banned for life.
In contrast, yesterday I opened Intel's new NUC for a project I am working on - beautifully made with quality workmanship, quality firmware, and quality design. Designed by skilled engineers no doubt. I fired it up and it worked a treat. Of course Intel is a big company, but they can call on the best engineers.
Some small companies can also go a great job, but their quality is only as good as the engineers they want to pay for, and of course the quality of their management. You pay peanuts, you get monkeys.