I'll try to answer my own question.
First of all I'd like to clear that in some cases I think
hreflang is basically mandatory:
When you are targeting two languages inside the same country. For example, french-speaking Canadian users search for your brand name. You would like them to see your
domain.ca/fr french page. And when English-speaking Canadian users do the same search, you need them to see
domain.ca/en in English. I think the main issue here is that both users performed the same query: "YOUR_BRAND_NAME", which is the same in both languages, so there is no other way for Google to know which page to show to them. Maybe your English page has a much higher ranking and your french page will never show up in results, unless you add those
hreflang and say to Google: "look, those pages are the same, pick the correct localized version to show".
Another case is when you are targeting two countries that speak the same language. For example:
MX (Mexico) and
ES (Spain). Now it doesn't even matter if they are searching for your brand name or not, because your whole content is basically duplicated. If your website is about "caballos" (horses in Spanish), users from Mexico and Spain will search for "caballos" and you'd like Google to show them the correct localized version. Again, I think the main issue here is that users will search for the exact same queries in both countries.
I will elaborate more on this subject. For example, in this video from International Search Summit Barcelona 2017, Gary Illyes, from Google, says something like that:
hreflang what you are doing is telling that pages in a cluster (..). then those pages should be able to use each other ranking signals. Essentially, if you have a page in English that does really well in an English market, and you have a page in Spanish (...) normally, without
hreflang, it doesn't mean that your Spanish page will do well in Spanish Google. Basically, that Spanish page, without
hreflang, will have to collect the links and all the other ranking signals (...) on its own, to rank well.
hreflang you can tell us that: "here are two pages that are close to equivalent. Share the ranking signals between the two". So basically if someone will search for a term that would show the English page really high, then if the user's language is Spanish , then we would actually promote the Spanish language version using the signals from the English version
I think the key point of what he said was: "if someone will search for a term that would show the English page really high". That's why I think it's all about if your users in different targets will perform the exact same queries or not.
And that's why I mentioned those cases where I think is mandatory to implement
- I think that searches for the exact same queries would mostly happen when you have a strong brand name that people will search for, given the fact that your brand name will not change across regions.
- Or it will definitely happen when you target different markets with the same language, like the Mexico and Spain example from above, or US, UK and AU, etc. Because users' queries would be exactly the same and you would benefit from the
hreflang like he says.
Conversely, I think that if your website does not have a strong brand name (i.e: you don't expect people searching for your brand name) and it's being fully translated to another country/region, and you don't expect your users' queries to be the same at all, there is no point in implementing
For example: an English website about
"horses", you expect people searching for the term
"horses". When you translate it to Spanish, you want to be shown to people searching for
"caballos". If a Spanish users searches for
"horses" he/she probably wants to see the English version of your page anyway, and not the Spanish one, like the example Gary mentions in his talk.
So the bottom line is: in that other country/region, will users query for your pages in the exact same terms? If so, then you probably need to add the
hreflang tags. Otherwise, you probably don't.
The Moz guide for international SEO seems to agree with what I'm saying here: