Following this line of thought - sacrificed alot and you now own a house (shocking in this market I know). Its value goes up 100k in a year due to forces out of your control. You now owe 30k in additional tax.
Should you now be forced to sell your home if you can’t pay this tax?
Following it further- you have a bank account. You save 20k. You now have an asset that is increasing in value - do you now owe tax on this?
There is a bloody good reason taxes are paid when gains are realised, or more accurately when money changes hands.