It's great you are studying to be an engineer in Ireland. Your question is complicated, and know first of all that this is a big research area that many people have been studying since the 1970's! Luckily though, there are many resources where we can learn more about this complicated issue.
Dr. Virginia Valian published a book in 1998 titled, "Why so slow: The Advancement of Women" specifically about why the advancement of women in the sciences and engineering has been slow. Her ideas are still incredibly valid today in 2013, and she has given extensive talks explaining the ideas of her book. MIT Press has a video here:
http://video.mit.edu/watch/why-so-slow-the-advancement-of-women-virginia-valian-6901/ and an interview with her in the NY Times is here: http://www.nytimes.com/1998/08/25/science/conversation-with-virginia-valian-exploring-gender-gap-absence-equality.html?pagewanted=all&src=pm
In fact, the NY Times loves writing about the lack of women in science/engineering - in October 2013 they published this article discussing some of the reasons there are not many women in these fields: http://www.nytimes.com/2013/10/06/magazine/why-are-there-still-so-few-women-in-science.html?_r=0
On a more academic note, the Association of American University Women (AAUW) published a report in Feb 2013 with a similar title, "Why so few: Women in Science, Technology, Engineering, Mathematics". This report, and their website in general, are great resources for learning more about women in STEM fields. See: http://www.aauw.org/files/2013/02/Why-So-Few-Women-in-Science-Technology-Engineering-and-Mathematics-executive-summary.pdf
And in general - there are many different studies and ideas out there in general looking at various reasons why there aren't more women in engineering, or why women leave engineering or don't consider it an option. You can read pretty endlessly about what other people think on this issue - but at the end of the day, what do YOU think? Your personal experiences and your local context may be significant variables that you can bring to explaining why you think there aren't more women in engineering where you are. Great question, and good luck in Ireland :)