phpbb is now and has been for years, the most popular bulletin board system in the world, free or paid.
so, I kind of doubt that not having something like a "like' system as default will really hurt phpbb at all.
and, you statement that
All forums of the world have it
is simply not true.
considering the hundreds of thousands of phpbb users that never come here and don't even know what a MOD is and therefore have never installed a "thanks" or "like" MOD, I would have to say the the majority of phpbb users don't really care about it.
now, having said all that, there are many many requests for this type of MOD and now extension.
however, the whole point of phpbb has always been to keep it to the basics of a bulletin board /dicusssion board system. if you want that type of add on then you can install it. however, the rest of us that don't care about this type of thing do not have to have our boards all cluttered up with unwanted bloat.