Defragmenter programs can delete System Restore Points

I've been mostly using Win 8.1 lately and see some "interesting" findings.
I prefer Win 7, but some people I help are buying Win 8 PCs, and then call me for help.
So, I've got Win 8.1 now and I'm trying to learn as much as possible.
I don't want this post to start a Win 7/Win 8 flame war.
If I'm going "off-topic" with this, let me know and I'll delete this post ...

On this Win 8.1 OS

I know there was at least one Restore Point (last I checked).
There are none now.
The space allocated for RPs was reset to 0, I know I set that to apx 10% earlier.

I NEVER installed a 3rd party defrag utility on this OS.
I NEVER manually ran a defrag, I let Windows default scheduled defrag handle this.

Just checked and SOMETHING defragged the [C] partiton ONLY a day after the scheduled defrag.
It was NOT the default Scheduled Defrag Task that ran, I have History enabled.

I do use CCleaner file cleaner.
I have been installing several programs and testing them, but the system is "clean" imho.

If this thread is for Win 7 only, I can delete this post.
If anyone is interested in Win 8 "issues", this is what I found so far.
I didn't see a thread about this issue on EF, but maybe this info will help over there ...

The more I look at this the more interesting - and confusing ...
The ScheduledDefrag task in Win 8.1 has NO triggers. (see screen print 1)
The ScheduledDefrag task in Win 7 HAS a trigger.

In Win 8.1 Task History you can see the task ran on 5/26 and then on 5/29... (see screen print 2)
From what I see the defrag task runs every couple of days, not once a week (as I expected).
In Win 7 the defrag task runs once a week - as it should.

In Event History I found 2 defrag "Optimizer" events that ran on 5/27. (see screen print 3)
What ran to cause these events ????

The "event text" for these is:
The storage optimizer successfully completed boot optimization on SSF3A-1 Win8.1 (C)
The storage optimizer successfully completed analysis on SSF3A-1 Win8.1 (C)

I did find Shawn's tutorials in EF
Optimize Drives - Defrag HDD and TRIM SSD in Windows 8
Optimize Drives Schedule - Change in Windows 8

but I don't understand why "defrag/optimize" runs every couple of days and not weekly (see screen print 4)
And, what runs to cause the optimizer events that aren't listed in the defrag task history

I don't have a RPLifeInterval registry key in Win 8.1.
I checked again and the Restore Point is gone and System Restore max usage is reset to 0.

For now:
I set the max usage back to 10%.
I turned off scheduled defrag.
I'll keep an eye on it and see how it goes the next few days ...

No - this system is TRIPLE boot.
:)