Because these terms have meaning and it's important. Something can't just kind of be a genocide, it's one of the greatest crimes that can be committed. There has to be a higher requirement for evidence than "well, some people were killed".
Let's look at other genocides happening today.
Gaza:
The official position of the Israeli government is to kill Palestinians en masse, including women and children, expropriate their land by force, and impose conditions designed to exterminate them through blockades, denying them food and medical supplies, etc.
That's a clear-cut genocide.
Ukraine:
Russia has killed civilians en masse, including women and children, it has targeted infrastructure like food and electricity with the intent to impose unlivable conditions. In occupied areas, it is official Russian policy to kill or expel Ukrainians and replace them with foreign populations from central Asia. They've also abducted children from the group and transferred them to Russian families.
That's a genocide, albeit a smaller-scale and more inept one because Russia controls so little of Ukraine.
South Africa:
Based on what I know, over a period of decades, Boers have been targeted by criminal groups and have faced a disproportionate amount of violence. It is the SA government's official position to transfer wealth and land from Boers to black farmers.
If these attacks are sponsored by the government, that would be much closer to a genocide, but I haven't seen proof of that. To me, it just looks like widespread crime targeting the wealthy, many of whom are Boers.
This is still a very bad situation, but it seems closer to what the Soviets did to the Kulaks to me. It's a class-based attack targeting wealthy farmers committed by lower classes out of jealousy or scapegoating.
Would you say that SA is intentionally imposing unlivable conditions on the Boers? Even if they might not be perpetrating the farm attacks, is the government doing other things to make life harder?