Why? Because he's overpaid for the role he plays with us, and with our talent at WR he won't see the field ever. Not only that, a KR/PR is easy to replace and we likely have one or two on our roster RIGHT NOW. The Bills would be remiss not to get value for a guy who is, as much as a few fools would deny this, expendable and easily replaceable. Getting value for him would allow the bills to expand the TALENT on the team by moving up in the draft or using the picks gained to get another solid veteran at another position.
Parrish is replaceable on KR/PR by both McGee AND McKelvin. He's replaceable at WR by any WR currently on Buffalo's roster because Parrish has done nothing at WR.
I'm not saying that I don't think Parrish can be electrifying and is a fantastic returner - he is. I'm just saying it would be wise to get value for a guy who is expendable and might not make the team, anyway.
For all the bitching people do about how the Bills are never like the patriots in their personnel moves, this is one instance where they are doing EXACTLY what the patriots do. They are interested in getting value for an overpaid player, who has a replacement (or two) right on the roster. Makes perfect sense.