Will said:
It's a point about flexibility.
The problem is that flexibility requires the ability to change your role quickly and have a large variety of special abilities at your disposal.
Bards can do all the things you mention. However, they have so few spells known that they are forced to choose only a couple of options which reduces their flexibility. Since they are spontaneous casters they can't change their spell list depending on what sort of adventure they are going on. If they are on a dungeon crawl they will have to expect that charm person is going to be a wasted slot for 90% of the game. If they are in a social adventure then haste will be useless more often.
Sure, a bard can cast healing...poorly. When the fighter takes 80 damage during a round, the bard's healing isn't going to cut it no matter how high level he is. At that point the cleric HAS to be the one to heal the fighter.
The thing about versatility is that if you can cast Haste or Glitterdust and someone else can cast both of those AND Fireball, they are more versatile than you are. If, on any given round, the best choice is to do something other than haste or glittterdust then you are less powerful.
Casting Mage Armor isn't that big of a deal once you are level 8 and higher. Most adventuring parties go to sleep after 8 hours. Plus 1st level spells are coming out of their ears and they never run out of them. The ability to wear poor armor isn't a big deal.
Fascination and Suggestion are so limited in use they might as well not even be listed. I mean you have to get someone to sit there and listen to you sing/play music and pay attention to you for over a minute straight willingly before they even have to make a save against fascination.
Will said:
Flexibility is important.
Yes, a barbarian can do more damage, the wizard has Haste, the cleric has Silence and healing, and the rogue can sneak.
But if any of those three are disabled, busy, or need help? The bard can do it all while making everyone better at the same time. He's unpopular because he doesn't shine, but he's cool because he's always there, making that one bit of difference.
And this is actually my key point as well. The bard doesn't do anything himself. He does what other people do...poorly. IF they are disabled he might be able to shine for a while as "good enough for now" but with any other character around he is sub par and is about making the other people look better.
The thing is that you can do 90% of what the Bard can do by playing either a wizard or cleric. What you lose from the last 10% you instead gain a large list of stuff that the bard CAN'T do that is easily 10 times more powerful than the 10% you are losing.
As a cleric you might not be able to cast haste and glitterdust, or use bardic knowledge, or bardic songs. In exchange you get to wear full plate, get more hit points, the ability to heal MUCH better, spells like Righteous Wrath of the Faithful, Prayer, Recitation, Divine Power, Righteous Might, Protection from Energy, Flame Strike, Raise Dead...and so on. Some of these spells give bonuses close to or better than bardic music. Righteous Wrath is really close to being able to cast haste, and you can turn yourself into a better fighter than the fighter is.
As a wizard you might not be able to heal, use bardic knowledge or songs, or wear light armor. In exchange you get an entire suite of damaging and paralyzing spells. The ability to change all of your spells around every day, to cast more of them per day, the ability to fly, teleport, protect yourself from damage, and much, much more. Pretty much you get close to all the same buffing spells as the bard and some of them earlier than the bard does. The only difference in your buffing ability to a bard is bardic music which doesn't stack with Bless, Recitation, Heroes Feast. So often its ability is redundant and useless.
It isn't so much a matter of not being the one up front shining. It's that if you are looking to play a leader type that Cleric is a much better choice overall. It needs to be more equal. Mainly, you need to be able to heal just as well as the cleric to be on equal footing with them and bardic music needs to be ramped up to be more powerful.