The problem is that the only reasoning your bias will allow is what you presume to be 'objectively relevant'. And as you have just admitted, there is no 'objective' evidence (or reason) to make any presumptions regarding purpose, at all. Even though you are clearly doing so, anyway. However, there can still be subjective evidence, and reasoning, for choosing to adopt the presumption that more than chance is at work in the web of cause and effect that existence seems to adhere to.
Let's say one is able to appreciate the 'gift' of being who and where they are because they've chosen to perceive their own existence as being the result of something more than an 'accident of chance'. And not only is their experience of life better for it, but their positive effect on others is increased as well. Wouldn't this, then, be a reasonable argument for adopting such a proposition, especially when there is no 'objective' reason or evidence to contradict that proposition? And meanwhile, where is the subjective value to be gained by adopting the proposition that everything that happens is ultimately just the result chance, and that there is no significant meaning or purpose to any of it?
The problem with being so biased in favor of "objectivism" is that value is subjective, not objective. So that when one's bias excludes subjective experience as being irrelevant, one is excluding that which generates value. And what a sad way that would be, to live!