Let's check it out!
In short, SEO meta keywords look like that:
<meta name="keywords" content="keyword1, keyword2">
This meta is supposed to add pertinent information for search engines. As you might guess, there have been many abusing techniques, but we won't see those dark lords (a.k.a black hats) tricks from the ancient ages.
I will use the term "keywords" all the time in this short article. I could also write "search queries" or "search terms".
When I say "target some keywords", it means you optimize your page for search queries, what people type in search engines.
As a result, keywords are essential elements for your SEO and ranking, and it won't probably change in the next years.
However, it does not mean you have to write a specific meta to tell everybody, including Google, what you want to achieve.
Does Google use the meta to rank websites in search results?
In 2009, Google's answer was no:
They simply don't have any effect in our search ranking at present
At this time, Google considered keywords meta as an "off-page factor", which means something the user does not see. Yet, backlinks are off-page signals and, as far as I know, it's a ranking factor.
The main reason is that there were so many abuses, such as stuffing with irrelevant keywords, that they cannot reasonably take it into their algorithm.
Google holds approximately 92% of the market (source: Google ^^), so if Google skips it, you should probably do the same.
Besides, it's on the source page, so SEO specialists can read it and know which keywords your page targets. There are many other ways to retrieve that information, but this one is without question the most inexpensive.
If you look into the source page of Amazon.com in 2020, you will see something like that:
<meta name="keywords" content="Amazon, Amazon.com, Books, Online Shopping, Book Store, Magazine, Subscription, Music, CDs, DVDs, Videos, Electronics, Video Games, Computers, Cell Phones, Toys, Games, Apparel, Accessories, Shoes, Jewelry, Watches, Office Products, Sports & Outdoors, Sporting Goods, Baby Products, Health, Personal Care, Beauty, Home, Garden, Bed & Bath, Furniture, Tools, Hardware, Vacuums, Outdoor Living, Automotive Parts, Pet Supplies, Broadband, DSL">
So, on the one hand, everybody's telling you to skip the use of meta keywords, but on the other hand, if Amazon still uses it, maybe it's not so irrelevant.
Google, Bing, Baidu, and other search engines explicitly declare they don't use the meta to rank search results.
Only Yandex, a Russian search engine, still uses it.
However, it's less than 1% of the market (source Google). Even old search engines such as Altavista dropped support for keywords several years ago.
If you look at the WordPress ecosystem (the most popular CMS of all time), the most popular SEO plugin (Yoast) dropped support for meta keywords in 2018.
So why the hell does Amazon still use this meta?
After doing some researches, I realized the question was irrelevant. Let's rephrase it:
It's not because Amazon still uses it that it's relevant for SERPs (Search Engine Results Pages).
You don't need the meta keywords.