My big reason would be "it hurts readability". That is, when writing code, readibility for others who aren't familiar with it (including future me) is my top-priority, and that means indentation and alignment are HIGHLY important, and if I spend the time to write code with specific indentation and alignment, to make it readable at a glance, I want to be certain that it's always going to display exactly that way. Tabs specifically break that guarantee, because they're subject to editor settings, which means shit like the below example can occur:

I write the following code with an editor that uses a tab size of 4.

myObject.DoSomething(
    someParameter:      "A",
    someOtherParameter: "B",
    value:              "C");

If someone pulls this up in an editor that uses a tab size of 8, they get...

myObject.DoSomething(
    someParameter:          "A",
    someOtherParameter:     "B",
    value:                          "C");

Not really a big deal, in this simple case, but it illustrates the point.

My second reason would be that it makes code more difficult to WRITE, I.E. it's not that hard to insert spaces when you mean to insert tabs, considering that you're not LITERALLY using only tabs just only tabs for indentation and alignment. And if you do accidentally have spaces mixed in, you're not going to be able to tell. The guy on another machine with different editor settings will, though.

I'm aware there are fonts that can make spaces and tabs visible and distinct, but that sounds like a NIGHTMARE to write and read code with. I mentioned above, my top priority is easy readability, and introducing more visual noise to make tabs and spaces distinct can only hurt readability.

Because when I move left in tabs, the cursor isn't clear which tab I'm on. It also tried to sit off the left edge of a terminal in some editors because it aligns with the right side of the character (the tab), instead of the left.

I do see how tabs are a better option : they allow the one editing the file to decide how wide the indentation is. That's actually good User Interface design, by separating the data from the rendering layout.

I can see the argument both ways, but I like to use spaces so the visual and editing interfaces are more standard.