They're going to click on the first search result automatically, and if that happens to be your ad, then you just wasted $0.50-$5.00.
Another issue is keyword match types. If you used the keywords exactly as in the spreadsheet, without any modifiers, then you're giving Google way too much leeway in how they interpret and match search queries to your target keywords. For example, your keyword might be UPLOADCARE REVIEW but your ad will show for the search "uploading review" (I'm just guessing).
You might think "well even if our ad shows for an irrelevant keyword, surely the user would see the difference and not click on it!" Wrong. People click the first X results automatically.
Case in point: A data science platform company I consult once targeted python programmers. Instead they were getting tons of clicks from snake enthusiasts, before I got involved. Oops.
Another company was selling monitoring software for mobile apps but was paying Google (inadvertently) for searchers of free mobile apps. Oops.[1]
Anyway, the other lessons mentioned are still valid, but I feel the biggest lesson (mistake?) was overlooked.
[1] Quick tip if you're running Google Ads now: Go to your Keywords Report and click on the Search Terms tab. You'll see the actual search terms people used before they saw your ad. If they vary wildly from your target keywords, you need to fix your keyword targeting.
PS - More fun "Oops" stories about Google Ads: https://www.gkogan.co/blog/selling-software-snake-charmers/