In short,
Google is getting better at design faster than Apple is getting better at web services.
Patrick Gibson argues that Apple’s web services skills haven’t improved that much and it would gain so much by acquiring Twitter, not for the technology or the services, but for the skills of the people running Twitter. It has improved greatly in handling massive surges of traffic, getting its apps in sync, and quick at introducing features. When you’re talking about scale, few companies are better at it than Facebook and Google and Twitter is perhaps the largest and most visible one that Apple can afford.
On the other hand, for just about every other reason, it’s not a good idea for Apple to buy Twitter. If employee retention is Apple’s problem when it comes to top web talent as Gibson argues, that is something that Apple should focus on rather than acquiring another company.