there are many reasons: educational, cultural, communication, media, accessibility in person to contact and interact, occupation, geographical conditions, social environment, community based activities and involvement, parental input and peer group situation, self feeling perception and level of concern about the social development are major. 

Despite the motivations and influences, significant obstacles exist that, prevent participation of youths in community development are a lack of communication and awareness of opportunities, weak cooperation among organizations competing for youth participants, youth fears of speaking out, lack of diversity, systematic mistreatment of youth simply because of their age.

Other factors such as lack of transportation, lack of time, and not being sure of the benefits of their contributions can limit the active participation of youths. Other barriers are: lack of interesting programs, and cost.  

We evaluated community development programs and found that transportation was the key factor -- the schools did not provide transportation after the school day and the students did not want to walk home through unsafe neighborhoods. Also, just because you provide youth with an opportunity does not mean that they know how to take advantage of the opportunity. 

I believe you have some high quality answers presented here already. One hopes that any social or community programming is based on the needs of the population to which the programs are being delivered. Youth from one neighborhood may not face exactly the same challenges as youth from another therefore knowing the population is key to developing community programs. Another aspect to consider is engagement of the parents or guardians of the youth population. How much do they know about community programs and do they feel it will be beneficial for their child? One more thought, exposure and communication is also important. Your target population needs to know the program exists in order to fully engage.

In addition to what has been said already, there is need for sense of belonging, communication and making them the target of the program, cos young people this days dose not engage in anything of no benefit to them. I believe that can go a long way to motivate them to participate.