Why is Golden St not the favorite?

A team with a high point differential, a good coach, a good defense, should be regarded as a heavy favorite to win a title. Add to this having an MVP candidate, Curry, to the "best player on the court usually wins" theory.

As a comparison. Currently GS's SRS rating (a combination of schedule strength and margin of victory) stands at 9.87, which is one of the highest of all time. The Celtics highest rating is around 9.3, and nearly every time they have been over or around 7.5 they have won a title (one exception was 2009 when Garnett was hurt). The 6 Bulls titles, the lowest came in at around a 6 (the year they beat the Suns). Three came in over a 10. This is a common theme to see "Won Finals" next to a very highly rated team.

There was only one team I could identify that was in the same elite ballpark, over a high 8 or low 9 and did not win a title with a "clear path" (no better team around).

The 2008-09 Cavs, who were upset by Orlando in the conference finals (but probably would have lost to a healthy Celtics team also).

There are several teams in the high 7 or low 8 range that lost however.

88-89 Cavs - "the Shot", Bulls upset them in the first round
02-03 Mavericks - lost to the Spurs in the conference finals. Note this was not the 06-07 team that lost to Golden St in the first round, or the 05-06 team that lost in the Finals.
72-73 Lakers - lost to the Knicks in the Finals
71-72 Bucks - this is the only team over a 10 that lost. And they lost to an even better Lakers team in the conference Finals.
85-86 Bucks - swept by an even better Celtics team in the conference Finals
72-73 Bucks - upset by the Warriors in conference semis
73-74 Bucks - lost in the Finals to the Celtics. If you are sensing a theme here, the answer is "Kareem was on the wrong team".
12-13 Thunder - lost in conference semis to Grizzlies, Westbrook got hurt the round before. Very good Spurs-Thunder and Heat-Thunder rematches were denied by that injury.
93-94 Sonics - upset by the Nuggets in the first round, probably the most improbable first round upset in NBA history.
94-95 Sonics - upset by the Lakers in the first round, probably the second most improbable, except the Lakers were a #5 seed (looking at their roster, I have no idea how).
67-68 Sixers - lost to Celtics in conference Finals
80-81 Sixers - lost to Celtics in conference Finals
90-91 Blazers - lost to Lakers in conference Finals, Bulls were better than both that year anyway.
01-02 Kings - lost to Lakers in conference Finals in one of the series widely considered tainted by an officiating scandal.
00-01 Spurs - swept by Lakers in conference Finals
03-04 Spurs - lost to Lakers in conference semis
96-97 Jazz - lost to Bulls in Finals, Bulls were much better anyway
94-95 Jazz - lost to Rockets in first round

A theme to these: either they lost to a better team in many cases or lost to specific teams (Lakers, Celtics, Bulls) that were likely to have gone on to win and in most cases were reasonably close in competitive value. The Warriors have no one in that range. Should they be pretty healthy, I see no reason not to favor them in the playoffs.