They are not. You will have to put up some really crazy explanation to define Microsoft as risky.
Generally companies without a solid business are risky. Netflix IS there - their idea is very valid (customer myself, I love them), but they run a hughhuge deficit and it is unclear whether this will play out or not. Tesla is risky - the concept is amazing, but look at how much moenymoney they burn and how high their debts are.
Amazon - so far they quite nicely manage to reinvest their huge profits, but they (a) are profitable, (b) it is not something others can easily copy (logistics centers) and (c) they have some income streams (like microsoftMicrosoft, azureAzure turns into a huge profit center).
Compare that to Apple - (a) very profitable, (b) unclear how the future looks as they (c) mostly depend on one income stream (iphone sales). While I would be sure they survive as a company, I sort of love saying there is no way to justify their price and unless they come up with alternative revenue streams, their upside is limited.
Unproven companies with mostly unproven business models are risky. One trick ponies are risky. Many of those are in tech.
The point about tech companies is that most (a) are unrprovenunproven and often come with (b) unproven models. Also (c) they can easily get sidetracked. Look at AMD - they have an amazing processor lineup now. Many years ago their Bulldozer architecture flopped and it took them a long time - and doubting their survivability - until they managed to pull off the ZEN architecture. High risk - one wrong step and you may lose a lot of money.