I really wish people wouldn't say this - it makes zero business sense. Here are some rough numbers to illustrate why:
Apple sold around 18 million Macs last year, generating about $23 billion in sales. Apple's share of the PC market is around 7.5% (and growing). There are around 240 million PCs being sold per year at the moment and the total market is worth something like $200 billion.
Even if the PC market halves over the next 10 years that still means sales of 1.8 billion PCs over the next 10 years. If Apple can grab 10% of those sales over the next 10 years, which is doable, it stands to make sales of
$230 billion over the next 10 years. Sorry, but that's not small change, even for Apple. If they really pulled their fingers out of their asses and took 15% of the market, and PC sales remained stable at today's numbers, they could make sales of
$460 billion over the next ten years. But they need to fight for that, which they are clearly not doing at the moment.
The Apple Watch, by comparison, is selling around 10 million units a year, at let's say $400 each on average, which means $4 billion in sales per year. And these sales are FALLING drastically (much harder than PC sales). See:
So no... it makes NO SENSE for Apple to focus on watches instead of Macs, unless you think the watches will magically start selling at least 10x more than they do today. Right now they are ignoring a cash cow to focus on a failed project.