@IsItSnowing
What does “Sharing” mean in this context though? He has made investments- with his own share of discretionary spending money- and is content to keep them as investments, drawing down small amounts for particular things he wants. He is probably wise to do this, as if he withdraws large sums at once he will pay tax on it. He may well actually be better off keeping his investment intact rather than paying down a mortgage, depending on the interest rate differential. I.e. if he is getting 6% return on his investment vs 3% on the mortgage he is earning more keeping the money where it is vs reducing the mortgage. Either way it’s his investment to decide to spend or keep, as he wishes. It’s not OP’s capital and she doesn’t get a say. I think she is wrong to think she does. If she has savings, does he have right of access to them to (outside of a divorce settlement)? Does he get a say on how OP spends her “fun money”?
I don’t think it is the same as lottery ticket- a lottery ticket is minimal spending, no real risk- I’d say spouses should share lottery wins equally. Savings and investments are different, IMO, if the capital has come from an individual’s own allocated proportion of disposable income (assuming that allocation had been fairly done and mutually agreed upon). If OP’s DH has made a significant amount he probably will have had to have either build this up over time (smaller amounts in the long-term) or had a big enough pot to start with; and he will probably have had put in a fair bit of effort in to it. He is unlikely just to have got extremely lucky with one small investment which he has not thought about or done anything to manage since making an impulsive decision to buy crypto/bitcoin/other investment- though it is impossible, I suppose.
Perhaps he does not want to spend the money on holidays or treats. He may not feel paying down the mortgage is a good option right now and he could be right (e.g. large withdrawals may well have tax implications, absorbing a significant proportion of the available capital; or he may be making more money than would be saved by paying down the mortgage). Perhaps he has a goal that he has set for himself or something he wishes to buy that otherwise could not be afforded, and he is using this to fund it- he is not asking op to sacrifice her spending or mutual savings goals in order to achieve this, so this is as entirely reasonable approach as op spending (or saving) her proportion of discretionary funds as she sees fit is.
At the end of the day, OP’s husband invested some of his own personal spending money, wisely in this case, but not without risk- and has increased his investment. He could have lost it all, too (and still could). It isn’t hers, she has spent her share of disposable income on things of her choosing (or indeed, if she has put it into an ISA or savings account)- as she is absolutely within her rights to do- but she can’t then come along and decide she wants his share to spend on a holiday or treats or even on the mortgage. If she wants that, she can either save some of her share of “fun money” and utilise it for the things she wants, OR if they both decide the need a holiday/more expensive holiday/a better car/pay off some of the mortgage, then they can both reduce their proportion of “fun money” equally to save to meet those joint goals. That’s what being a partnership would look like to me. Unilaterally deciding you have a say on your partners share of discretionary spending, whilst spending all of yours as you wish, is not a partnership.