The issue is other than ad words their other bets are not nearly as profitable.
PS: I suspect they probably spent less on self-driving cars than they gained back from that Halo.
In other words, by having so many diverse bets, investors in Alphabet have to buy into all of those bets. So the number of investors that believe in all of those bets is smaller than the sum of all investors that would invest in each one individually.
Google executives certainly think they're better and for the time being it seems investors agree.
It seems some* investors agree. There is no way to know how much more they could be worth if they were separate entities.