Why are wounds a good place for infections?

Do wounds or infections make it easier for bacteria to grow and stuff? Why are open cuts good candidates for infections?

First, an intact skin is the first barrier/defence against all infection. The moment it is disturbed it put the person at risk of acquiring an infection from the environment and even from his own skin flora.
It should be remembered that not all wound will get infected and there are various factors play in this matter. The nature of wound itself is very important as a predisposing factor. If the wound resulted in loss of major portion of skin and tissues , the chances are increasing. Contamination is another factor too. Once, microbes invade the area underneath the tissue, it breeds quickly as the environment underneath the tissue is warm, having plenty of oxygen or no oxygen(sometime lack of oxygen that favours the growth of microbes) and dark.
If your wound contains lot of debris(death tissues), it is another good source of multiplication.
There are other factors too that favour the growth such as any chronic illnesses like diabetes, vascular problems, malnutrition, drugs(steroids hinders the wound healing), and lack of treatment for the wound.
So, it is multifactorial and any wound that has occurred from a dirty source and resulted in loss of major portion of skin and tissues will require a proper attention to reduce the risk of infection. However, even a minor cut can have a great effect to the body due to infection, hence need not to be overlooked.
Hope, this helps.

they are open for all sorts of bacteria.

Blood and tissue make an excellent growth medium for bacteria plus an open wound has no blood circulation which means that bacteria can grow until an immune reaction starts to fight the infection.

Because they are "open". The skin is the body's first line of defense. So if it's cut or there is a wound, it's not covered by skin, thereby making it easy for bacteria to grow.

A wound is like an open door and makes it way easier for bacteria to grow. When your skin is intact, there are lots of layers of overlapping dead skin cells that protect your body from bacteria. When you have an open cut, those layers aren't there and bacteria can travel in and feed on all the nurtrients underneath. If the wound or the infection is really bad, bacteria can also travel into your bloodstream and cause a major infection throughout your body. Luckily, when we're healthy, we have white blood cells and other mechanisms that protect us from bacteria and other nasty little bugs. The body is an amazing thing!

Because wounds and open cuts are ideal breeding grounds for bacterias, and other organisms as they are often warm and moist and an ideal entry site into the blood stream.