I agree exactly! Involving fellow believers in the day to day needs we have - whether for physical healing, spiritual warfare, personal failings, family, friends, etc. - gives us a stake in each other's lives and we see our faith grow as we acknowledge Almighty God's hand in answering every concern we have. I just don't see that same kind of dynamic happening with prayers to the departed "Saints". There isn't a direct connection - we don't hear, see, touch, speak or otherwise have any assurance that our prayers are "being handled". When our petitions are NOT answered, we have nothing, no feedback, with which to determine WHY they weren't and how we could change in what we ask for.
I also believe it is God that receives ALL the glory, honor and praise when we involve others in interceding with us because we actually see specific requests get answered and we rejoice together in gratitude to our Lord and Savior for His mercy, grace and love and for caring about everything that concerns us. Putting such needs before an unseen, dead person - Saint or saint - just doesn't provide the same assurance of knowing HE hears us and will provide all our needs in Christ Jesus - and He is NEVER too busy.
Be anxious for nothing, but in everything by prayer and supplication with thanksgiving let your requests be made known to God. And the peace of God, which surpasses all comprehension, will guard your hearts and your minds in Christ Jesus. (Philippians 4:6,7)