dissolve in cold water, ONLY THEN add hot water. The rationale behind it is that aromatics evaporate too quickly when the instant powder is infused with too/boiling hot water.
In the UK it's still very common for people to have instant coffee at home. Companies will sometimes have their own fancy coffee maker (e.g. Nespresso) but not always.
It's kinda like asking "why don't more Americans own electric kettles?".
UK: Kettle for tea.
US: Coffee maker for coffee.
We generally drink more tea than coffee and so kettles became the norm. Some people do own their own coffee makers or cafetieres but it's less common. One is a nation coffee-drinkers and the other tea drinkers. Each has settled into using different machines and therefore different products.