Putting it simply, lawyers are not entitled to give financial advice and financial planners are not entitled to give legal advice. Estate planning is generally a mix of both financial and legal questions. For most clients if comprehensive advice is needed they will speak to both their solicitor and financial planner.
A part of estate planning from the legal perspective is ascertaining whether potential beneficiaries in your estate are or may be subject to legal claims. A simple example is where a potential beneficiary is an undischarged bankrupt. Any bequest of assets to a undischarged bankrupt immediately vests in the Trustee in Bankruptcy. This is unlikely to be the outcome the testator wishes.
Steps can be taken to avoid such a result such as simply excluding the bankrupt from the will or through the creation of a discretionary testamentary trust will.