Only because it doesn't fit your point.
If you don't have time to play the game. If the game isn't fun for you. Don't play it.
Unbelievable. Not only doesn't it fit my point it doesn't fit YOUR point. Or any point, really.
First of all, the mission timers have no bearing on whether the game is fun when you are playing it. The timers are too long to add any meaningful sense of urgency to a mission within the span of a given play session, so even if you have a problem with time limits, it probably doesn't impact (for or against) your sense of fun while you are actually playing.
The only thing the timers do is make it more annoying and cumbersome to STOP playing at your own convenience. It doesn't matter if you've been playing for 10 minutes or 10 hours; if you've been running missions during your play session then there's a good chance you'll have a few unfinished missions when it's time for you to stop playing. At that point you're stuck with a choice between playing past your intended time frame, or immediately making plans in real life for when you'll next be able to play the game so that you can finish the missions before the timers run out (oh and you *better* stick to that schedule and not do something dumb like allow other life requirements to interfere with your all-important play schedule otherwise "mission fail!"), or making peace with the fact that next time you log in you're immediately going to be bombarded with a bunch of "fail" notifications and angry "you suck!" messages from all the factions issuing those missions.
The solution according to you: when you play the game, always have in the back of your mind an awareness of when your play session is going to be ending, and how far off that moment is. Whenever you look at the mission board, you must accurately predict how long it will take you to complete this mission and any other missions you have already taken/are considering taking on. If there are any tempting missions which may exceed the scope of your current play session, you must also keep in mind what your real life schedule for the week looks like, and factor in whether you'll still have enough time to complete the mission during your next play session. If you leave the play session at any time for any reason, you must maintain an awareness of all the missions you had on your list, how far along your respective mission timers are, and make sure you log in and play again at an early enough time to complete the missions before the timers run out. Failure to do any of this perfectly and consistently will result in failure of the missions.
Sorry but I'd like to fail a mission because I lost the cargo, or was shot down by the assassin, or couldn't disable the target's drives before he jumped away. Not because I wasn't playing the game at a specific date and time.
If we had access to the statistics, I would be very surprised if the #1 reason for mission failure wasn't "timer ran out while i wasn't even playing."
How is this more immersive or realistic or whatever than the alternative? As things are now, you have to constantly be thinking about your life OUTSIDE of the game in order to properly play the game. If the timers froze in place when you logged off, you could be 100% invested in the goings-on INSIDE the game for the duration of your entire play session, however long or short it might be.
If things worked the way I am advocating, would you complain and demand it be switched back? Would you miss it? If so, why? Be honest here.