Because bard is just plain weak and giving other party members "support" does cover up these weakness. They hit like wet noodles outside of their openers or when their (long!) cooldowns are available.

Their songs are also lack luster.

Giving you back MP? Unless the healers are raising or DPSing like crazy, they should not need this. Casters have no issue either.

Giving you back TP? Unless major AoE madness is happening there should be no need for this. PLD/DRK suffer from TP but losing 10% DPS to keep a tank going is bad.

Boosting casting DPS? This one is good, no complaints. Ever better on battle voice.

Esuna + resist Song. Ha ha, outside of some very basic debuffs, this is downright insulting for a job to have for its level 50-60 arsenal. Any and all status ailments that actually matter cannot be cleaned! Not to mention that healers that know what they are doing should have no problem with cleansing and healing. We get more use out of this by using it on warriors' pacification than anything else!

Wanderer's Minuet? I don't consider this a song because it does not behave like a song, it behaves like an on/off buff with a drawbacks.

Swiftsong? The thing turns itself off when in battle! Its useful when solo but having to recast it every time you clear a mob in a dungeon is annoying. No uses in battles, downright terrible to recast in places like Palace of the Dead.

No song to boost melee DPS or haste. No songs for healing/regens. No songs to reduce damage. No songs with direct effects on enemies. Nothing good.

Lets just hope the new songs on the expansion have more to give than this.