Konami didnt immediately reply to a request for comment
With that out of the way let's talk about why
Not only does this synergize well with mana rocks and other artifacts with activated abilities, but it simultaneously functions as damage-based removal, a means of closing out a game, and a means of digging through your deck for key cards
While life gain does not directly help a player win a game, stalling an opponent's victory rather than contributing to that of a given player, lifelink is an excellent ability for decks that seek to pay life to activate abilities, or decks that seek to stall games in order to cast mana-intensive powerhouses
For example, if one World at War creates a second combat phase and a third main phase in a turn, then a second World at War is cast during that third main phase, no additional phases are created