First of all, from personal experience, motivational speeches and seminars were something I loved watching. They did motivated me, but the thing is - they do it for a while, and then you're back in your struggles, in your boring (or not so boring) life.
The reason why I think the motivational trend is like a candy with empty calories, to boost your mood for a few hours, is that they are impractical. No one can be motivated on a daily or hourly basis. Are you passionately motivated when you work on a difficult project? Ask those dedicated software engineers and programmers if they are motivated and bursting with passion and energy while they are stuck in their code, figuring out why it's broken. No, they are frustrated and I am sure, they hate their job at this moment.
And life is this most of the time. We struggle most of the time, and only in those tiny moments when we succeed are we the happiest. And the feeling can't be compared to the feelings of a person who attended a motivational seminar.
Hard work and success in your work are the best motivators you can ever have.
Right now, I would watch a motivational speech or seminar only if I need some mental recharge, to remind me that I am on the right track. Sometimes we lose confidence in ourselves, and a motivational speech will simply pick us up, and say 'Hey, you're not that bad, go on, you can do it'.
But today, motivational speeches are used with predominantly the wrong audience. The audience are people who need motivation to start something, to begin a project, to change their careers maybe, to work on a startup, etc. I am sure that these seminars were more like 'information bubbles' rather than motivational. They gather knowledge and ideas for their plans, and they don't hype themselves too much.
And again, like I said, if you ask professionals, startup managers, CEOs, etc. if they stay motivated all the time, I bet they will tell you they are just working hard to be where they are. And hard work isn't compatible with motivation. You just can't work properly and fruitfully if your heart is racing with joy and passion. At least not in my world. And don't get me wrong. I am passionate about what I do, but not in that crazy way when you can't focus your thoughts.
Motivational speeches take you to the 9th cloud, but hard work is on the Earth.
You need a cool head to be sure you'll do outstanding work! You can be motivated after work.
But me, as a freelancer - I don't have much time for motivation. The results of my hard work motivate me enough.