Why does God give us what he gives us?

Family, children, friends are given to to love. We need not make a demand upon them that they love us - but we should see each person in our circle of life as someone to love.
By loving each one we ought, we partner with God in allowing His divine love (Holy Spirit) to flow through us. The very spirit of revival is the Spirit of the Holy Spirit flowing through humanity to humanity. It is God having fellowship with others through us.
So why did God give "this one" or "that one" to you to love? Why has God withheld someone from you? Trusting God fully that "no good thing will He withhold from those who love Him" brings us not to the point of disappointment, but highest fulfillment. The lack of mates, children and friends is not a curse, but a stage in the journey to Christlikeness. When we grow in love, we also grow in family, friends and children. Christ guaranteed this in the gospels.
God also gives us unique people to love. When we find ourselves among "difficult to love" people we should ask, "What aspect or need of love does this person have that God has chosen me to supply for Him?" This is easy if we need only love for a moment. It is much more "loving" to be called to love these people for years and decades. :) We will find that most of those we are called to love for God, we are called to all the days of our lives. God has chosen us to live among them as He would.
Usually at the point of frustration in loving others is the point at which we are weak in Christlineness ourselves. The more we are transformed the "easier" it is to love. So our calling to love others is also a blessed tool of transformation!!! Do not be denied your transformation by pride, sloth, insecurity, greed or envy. Do not let the Devil himself to cheat you out of your transformation. Do not be hindered by envy, jealously, anger or foolishness.
When you are overwhelmed with all the need and demand of others for your love - rejoice. It is not "your love" they need or seek. It is God's love dispensed through you. These demands become your blessing as the need for bread for your neighbor leads you often to the dwelling of the Lord. Most always He requires us to "dine" with Him before we run off and do His will. Eph. 3:14-19