The old rub about "no taxation without representation" has something to it, historically.
In many instances, including England and France (and even Afghanistan), a democratically selected parliament was something offered by a monarch in exchange for securing popular approval for taxation.
Monarchies and dictatorship are the "ancestral state" of all democracies, and one strong incentive for them to abandon that power is that they can no longer support a government with rents and royalties from property, because the real driver of the economic system shifts to the entrepreneurship and labor of the masses.
Further, many of the monarchies that remain absolute and continue to have little or no democratic checks (e.g. Saudi Arabia and Kuwait) also have little or no domestic income taxation and instead raise most money through royalty/government owned property. Even Puerto Rico, a commonwealth within the United States that has no democratic input into the federal government (except non-voting representation) pays little or no federal tax by special arrangement.
Another reason that less democratic countries are less likely to have an income tax is a bit more complex.
One of the reasons that less developed countries, almost of which were begun with Western style democratic institutions, don't hold onto those institutions, is that they lack a sufficient corps of people to serve as skilled civil servants and potential politicians and top political appointees and judges to maintain a bureaucracy that can effectively govern a nation in the manner contemplated for a Western style democracy.
For example, this was an important reason that democratic institution collapsed in Sudan after it gained independence.
And, the corps of skilled people necessary to run a Western style democracy is also necessary to run a modern economy in which most economic transactions are conducted in the form of money transactions mediated through banks, and in which most people make their livelihood through employment in medium to large sized firms.
Countries without these kinds of economies, such as subsistence farming economies and economies that rely heavily on mining natural resources, tend to prevail in the absence of a population with these kinds of skills.
Also notably, countries without this kind of modern economy also tend to have more resources suitable for a national government to nationalize or own as royal property, and collect income from directly in lieu of taxation.
In the absence of a modern economy in which most economic transactions are conducted in the form of money transactions mediated through banks, and in which most people make their livelihood through employment in medium to large sized firms, it is extremely difficult to administer an efficient income tax with only modest tax evasion. Imposing an income tax on self-employed people requires lots of cooperation from the people being taxed and an ability to audit them through third-party records such as bank records.
Other kinds of taxes, such as property taxes, excise taxes on economically important industries, poll taxes, in kind labor levies, customs duties, and value added taxes are much easier to collect in the absence of massive cooperation from the people being taxed.
Therefore, since democracies and income taxes are favored in certain kinds of overlapping conditions, income taxes are more common in democracies than in non-democratic states where those conditions are frequently absent.
There are certainly exceptions. The District of Columbia has a modern economy but diminished democratic representation. So did Hong Kong. And, it is quite remarkable that India manages to maintain a fairly modern Western style democracy in an economy where 82% of employed people are self-employed. But, that doesn't take away from the general trend.