Because conditions in GW2 have three upsides to two downsides.
Downsides: 1. Damage over time is inferior to instant damage 2. Can be removed.
Upsides: 1. Damage is overall higher 2. Stat advantage ( Only 1 stat required VS 3 stats ) 3. Condi abilities generally have low tells and/or are heavily carried by uninteractive passives.
The answer, IMO, is to get rid of either the second or third advantage. Those two together are creating the problem where every single condi bunker build generally makes the game worse due to low interactivity combined with low player-skill requirements.
Anet needs to realize that the reason condi builds are so disliked has very little to do with how conditions actually work, but that the real reason is actually very similar to the reason most people do not like explosive entrance. EE is an instant cast passive that cannot be interrupted and automatically tags itself onto the next hit, which effectively turns the next attack -regardless of what that attack is- into a "must block/dodge". Many Condi abilities have a very similar bad design to them, such as "Deal X condi when you Deal Y Condi" passives, or "Instantly set foe on fire, zero cast time, zero animation", huge _unblockable_ AoEs, and of course everyone favorite "Randomly do Z condi when hitting". Skill design like this makes condi builds annoying to fight, not because they are DOT, but because the damage often comes from invisible or unclear sources.