d_s_f's comments merely reflect the way most nba viewers (viewers, not even fans) view the spurs. and he misses the gist of the question.
nba players do not view the spurs as "boring". they view them as "methodical", "precise", even "the best in the league". an invitation to join the spurs would please most nba vets (as that would mean they would get minutes) and would be tough for the rookies (as they would not only have to pass the physicals, preseason, regular season and d-league, plus the summer league next season).
as for the phoenix suns, joining them doesn't mean that much if you're not an all-star (or even an aging all-star) as most of their bench doesn't see the light of day much. you're there for insurance, not to contribute. this would severely discourage players who want to play (and encourage only those players who just want to be paid).
but for the spurs, even if you're not an all-star, they expect you to play, and play well. even if you're not a starter.