Best of 3 = more urgency / importance / excitement needed for playoff games.
too much travel
If it's only first round then at least it's guaranteed to be inter-conference so not traveling across several time zones.
This years first round matchups were Boston-Chicago, Cleveland-Indiana, Toronto-Milwaukee, Washington-Atlanta, GS-Portland, SA-Memphis, Houston-OKC, LAC-Utah, which are all (except Memphis which is geographically in the wrong conference) under three hours.
Also, it's the same exact amount of travel as games 5, 6, 7 in the current setup.