There are plenty of bug riddled pieces of software out there. Plenty of platforms. Most are probably unknown or not popular enough to be scrutinized. These 3 are the most popular, most used, and most targeted. You will see them in tech news more than any other pieces of software. If you read vulnerability and security blogs, you'll be exposed to a whole, new, enormous, and wonderful world of bug ridden software.
It's easy to say these kinds of things in hindsight. In their time, these systems became popular because they filled a void [1]. Now we look back and say "What were we thinking?", but it was harder to say back when the web browser was still a document system with minimal programmability.
In all reality, the craft of software engineering is still truly new to the world, and constantly, rapidly, changing. Unlike the material world with the limitations of space and resources, the abstract land of organizing information and information that works on information is a very hard problem to solve—if it's even "solvable" at all.
[1]: Well, okay, XP was kinda' forced onto the world.