Jury duty is a significant inconvenience. That said, if you want to be tried by a jury when you're accused of something, then you have to accept the price of occasionally serving on a jury. So, I think the goal is to design the system to minimize the inconvenience to the jury pool.
The thinking of the courts is probably, yes it is inconvenient for the person to be "on call" for a week, but at least that is better than being forced to sit at the courthouse for a week. Makes sense to me.
Now, only 90 minutes' notice to get to the court is certainly a lot less convenient that 1 day's notice. But there is probably a trade-off for convenience. Giving more notice probably means that more people will be called to actually come sit in the courthouse.
Think of it in manufacturing terms - there is a volatile and uncertain demand for jurors, the court's ability to forecast improves the closer you get to the date/hour, so longer notice means poorer forecasting and means the court needs more "buffer inventory" of jurors sitting in the courthouse.
For someone who gets summoned, what to do? If you're working, you simply warn co-workers etc that you are "on call" and don't schedule critical business stuff that week - if impossible then you reschedule your duty to a later date (every court I've heard of will permit that). If you get "called" then you go - by law, your employer cannot stop or punish you, and most of us aren't really as important as we think anyway - your company will probably survive your brief absence.
If you are a stay-at-home parent with small children, it may be possible to get excused.
Illinois Legal Aid | How Can I Get Out of Jury Duty? Otherwise, you or your spouse will have to make arrangements, that's all there is to it. Suppose your wife got H1N1 or broke her leg, and went in the hospital, you'd find a way to look after the kids, this is no different.
I've never been summoned for jury duty. When I was a lawyer, I really wanted to serve on a jury, as I thought it'd give me some insight, but I would have been kicked off any panel. Now I don't care either way, but I don't know if they'd still kick me off or not.