As I see it, the things that make an accountant more valuable to someone with a high income than a low income:
1) Deductions are "worth" more since they you pay a higher marginal rate (37% of $1 in the highest bracket is more than 10% of $1 in the lowest bracket), so if they catch something you miss you "make" more compared to their fees.
2) If the higher income comes from more complex employment like a business, or the potential to become reclassified as 1099 and be treated as a business (some doctors do this) so you can avoid some self employment taxes (s-corp).
3) Arguably your time is worth more that that of a lower income person (according to the market at least), so if you could be earning more in your area of expertise while your accountant is doing your taxes, or your free time is just worth more to you than their fee then it makes sense to use them.
But, there's nothing inherently different about high income that favors using an accountant compared to low income. If you're confident that you will find all the deductions you're entitled to, you can't work at something that will earn/save you more money (after taxes) than the accountant's fee, and you would rather save the money than have the extra time, then I'd agree with you that you don't really need an accountant. If any of those aren't true, then you might want to reconsider.