As ever on these threads, I can't understand how arrogant some people are to believe that whatever they think is easy to do; that the business itself hasn't already considered that. And dismissed it.
If they made a profit making you scrambled eggs when it's not on the menu, then they would,obviously, offer that.
It doesn't even matter why they can't, it doesn't take rocket science to assume it's a mixture of lack of facilities/time in this case, but it still doesn't matter, they've made a business decision they're not offering scrambled eggs for whatever reason, and that's it.
You arguing and complaining about it doesn't change that.
I've just looked it up. It's £3 for eggs on toast. Which are poached or fried. So, for £3 you think it makes business sense for them to employ someone to spend ten minutes trying to explain to a dim customer why they can't have it, then agreeing anyway and walking over to the supermarket aisle to get the eggs as they don't have them in the kitchen as they don't offer scrambled eggs. finding a bowl which they don't have and a whisk, filling in whatever forms are required ti transfer stock from shelf to kitchen, and cooking on a hob which they don't have; to serve to a customer who, given the nature of the question, is likely to continue to complain about the length of time it took.
Yabu.
And for future, if any business won't offer you something, they will have a reason for it.