My motherboard has 2 ram slots . Why does CPU-Z and Speccy show that I have 4 slots?

According to CPU-Z's documentation, the information it gathers from the motherboard is the following:

• Vendor, model and revision.
• BIOS model and date.
• Chipset (northbridge and southbridge) and sensor.
• Graphic interface.

CPU-Z shows 4 RAM slots since your motherboard's northbridge (Intel G41 Express Chipset) can handle up to 4 RAM modules.

The fact that Gigabyte decided to install only 2 RAM slots on this specific motherboard is simply not taken into account.

That's strange indeed, but the answers in this forum thread sound reasonable:

The chipset can probably handle four sticks, but the board only physically has two.

and

A lot of the inexpensive manufacturers will omit parts on the PCB itself to cut costs.

So, basically, CPU-Z and Speccy show to you what would be possible (using the information about/from the chipset), but the actual configuration the manufacturer chose can be different.