Because The Holy Spirit is not just going to give us the answer to everything. We have The Bible and we have brains God gave us. If it's a matter of sin/salvation then yes The Holy Spirit can talk to us but He's not going to tell us what to do or the answer to everything all the time
The Holy Spirit guilds us in all truth and conviction unless we quench His work in us. Growing in faith by seeking answers is part of the process when we walk with Him daily in truth. " Seek and ye shall find".
Be blessed.