When someone attacks you, they will find some middle ground of their own between delivering as much power as possible and maintaining as much balance and center as possible. One of the 'strategies' in Aikido is to encourage the attacker to choose a middle ground that leans as heavily as possible towards delivering power at the expense of balance. An uke who feels threatened our challenged is likely to opt for a safer attack with more balance. An uke who does not feel challenged, whose target is clear and open, who sees no obvious defense, no obvious 'fighting posture,' is more likely to opt for the delivery of power.
I had a teacher who said pretty often, "don't make your attacker any smarter than you have to."