IF, as you claim, the earth is really flat, then there ought to be a LOT of honest scientists willing to say so. They might be poor and scattered ..... and very probably not earning a living as geographers or astronomers but maybe as chemists or engineers or something else that isn't dependent on their opinion of the shape of the planet. But they ought to be out there somewhere. And yet they're not HERE on this website.
On other websites we can find scientists (of a sort, at least) who are adherents of some minority viewpoint - anti-vaccination, vegan diet, racist, into flying saucers, you name it - but a very definite paucity of scientists of any sort willing to declare themselves Flat Earthers.
Yet, if the Earth were flat and that fact were revealed, there would be a major economy boost to the economy of virtually every country. There'd be entirely new industries and technologies and sciences commenced to explore The Edge, go beyond The Edge, find new resources and even new life forms beyond The Edge, maybe even colonize the territory beyond The Edge, etc. It would be even more economically inspiring than the space race!
You're assuming there ought to be a lot of honest Scientists out there, your paradigm is that people are basically honest, but that's just your opinion, if people are basically just full of shit, then such a scheme would be easier to perpetrate.
People are afraid, they're afraid of standing out, of standing up.
Scientists especially spend all of their formative years being brainwashed, so they're not used to exercising independent thought, except for in very controlled, limited ways.
Most of them are easily herded, every once in a while you get a genius like Jung or Tesla, and often their genius is (initially) mistaken for insanity/folly, or they go unnoticed when in my estimation, and the estimation of some others, they deserved far more attention, like the Antoine Bechamps and Peter Duesbergs of the world, and those who carried on their work.
Most Scientists are afraid, afraid of being humiliated, of losing their credibility, their funds, their jobs, of taking chances, risks, putting it all on the line, most people from all walks of life play it safe, unless they have nothing left to lose, the so called geniuses of the world, it may not be so much a case of superior intelligence as superior courage, charisma and creativity.
Furthermore, there Are some flat earthers out there, not sure if they qualify as scientists, depends on how you define scientists, but there were serious researchers/theoreticians like Rowbotham, and many more before and after him.
There may be a few others both within and outside academia, but get almost 0 publicity.
Just because something is on the very fringes of Science, with almost 0 academic support and only a handful of independent researchers/theorists out there, doesn't guarantee it will never overtake the mainstream, it just makes it unlikely to occur, or anytime soon.
There may be Government Scientists exploring the edge in secret.
Given our track record, how we've made a mess of the known plane, they, including perhaps other sentient life forms out there who may be in control of or in collusion with government, they may be preventing us from making messes elsewhere.
It's not just about honesty, these matters are complicated, it's not obvious the earth is flat or round once you really delve into it, it may only be somewhat more probable that it's flat when you analyze all the data, but still ambiguous and open to debate, and so, it would be easier to convince most Scientists it's more likely it's round than flat if that's the case, only those at the very, very top of the Scientific/political establishment may know for absolute certain, because they have the resources to definitively test such matters.
If Science/State were to admit it's flat now, they would lose all credibility, other institutions on the fringe, people would begin turning away from the mainstream and towards the religious, philosophical and scientific fringes in droves, both Science and government would lose all their power and credibility, new institutions with different ways of organizing themselves and thought would rise up to challenge them, and humanity would enter a new age of chaos and revolution.
And, if there's nothing to explore on the edge of the Antarctic plateau, if it's just a barren, desolate wasteland, or an impenetrable dome, there may be no profits to be made, and so having the idea of outer space, and other planets to explore, gives them more of an excuse to tax the people.