At a certain point, there may be a need for an investor to delve into something that is certain to provide a faster return, perhaps in a short period of time.
Why? Isn't bitcoin potentially volatile enough? What more "faster return" is necessary, and at what point would a person "need" to engage in such extra risk taking, when bitcoin is already risky?
No doubt bitcoin is potentially volatile with its own peculiar risk and returns but investing (diversifying) in other different projects that's not cryptocurrency is another form of expansion that returns made from there can be utilize into accumulating and increasing your bitcoin portfolio, in my opinion a good diversification can be a supportive ground for a bitcoin investor not to tamper with his bitcoin investment at any financial emergency storm that might hit.
If the money is there enough to diversify the risk factor shouldn't be an excuse not to diversify. None diversification of businesses is like driving a car on along journey without having a spare tire with you for flat tire emergency along the long.
Be careful in mixing your metaphors too much.
One of the advantages of bitcoin remains position size, and if you go into a business, you usually will have a lot of upfront costs and time investments too.
With bitcoin you can adjust the the amount that you buy regularly, and you can also make sure that you have a sufficient extra cashflow for both income replacement and also emergencies.. ..so the mere fact that you don't diversify further is not the same as driving without a spare tire because hopefully you have already figured out your various amounts, and as you continue to build your bitcoin, there may be points in which diversification is starting to make sense, especially if you might start to have a couple of years of income within your cash reserves and your BTC investment.. but how you go about adding other ways of diversifying can be quite varied in how people might do it, whether they continue to buy BTC and then add other things that they are buying or if they slow down on their BTC buying or if they stop it completely... but it might be possible to make lump sum investments in some other assets, whether it is stock or property or something else (should not be shitcoins unless it is limited to small amounts such as less than 10%) so that your total value is not just in bitcoin and cash.